diff --git a/docs/membership-contract.md b/docs/membership-contract.md
index 564c9e7..fa28c5c 100644
--- a/docs/membership-contract.md
+++ b/docs/membership-contract.md
@@ -33,9 +33,15 @@
 1. 应用迁移 `20261028090000_membership_contracts`（仅新增表与 `orders.contract_accepted_at` 列），生成 Prisma Client，再发布 shared/server。
 2. 新增依赖 `pdfkit`；中文字体随服务端发布在 `packages/server/assets/fonts/NotoSansSC-Regular.otf`（SIL OFL）。可用环境变量 `CONTRACT_PDF_FONT_PATH` 指向其他字体。
 3. 小程序后台「开发管理 - 服务器域名」需将 API 域名加入 **downloadFile 合法域名**，否则无法导出 PDF。
-4. 发布前由馆主在「管理中心 - 合同签署设置」填写经营者名称、统一社会信用代码、经营者、联系电话、经营场所，并手写经营者签名。未完善时学员可查看但不能签署。
+4. 发布前由馆主在「管理中心 - 合同签署设置」填写经营者名称、统一社会信用代码、经营者、联系电话、经营场所。默认合同专用章见下方，经营者手写签名选填。未完善基本信息时学员可查看但不能签署。
 5. 发布新版小程序。旧版小程序购卡不会勾选同意，但仍会生成待签合同，并在新版个人中心提示签署。
 
+### 默认乙方合同章
+
+- 场馆提供的原图保存在 `packages/server/assets/contracts/party-b-seal.jpg`，发布服务端时须连同 `assets/` 一起部署（与 PDF 字体一致）。无需新增环境变量或数据库迁移。
+- 合同设置显示默认章；购买前范本、待签合同及签署阅读页在乙方签章区展示，经营者手写签名仍可选填并同时展示。
+- 签署时合同章以 data URI 写入合同正文 `document.partyBSeal`，纳入 SHA-256 校验并冻结；详情和 PDF 只使用该快照。替换默认图片后，仅影响未签合同，已签旧合同不追补印章。
+
 ## 回退
 
 - 服务端回退到上一版本即可，新增表保留不影响旧代码；不要删除 `membership_contracts`、`contract_events`，它们是签署凭证。
diff --git a/packages/app/src/components/ContractDocumentView.vue b/packages/app/src/components/ContractDocumentView.vue
index d1c95e1..8004eea 100644
--- a/packages/app/src/components/ContractDocumentView.vue
+++ b/packages/app/src/components/ContractDocumentView.vue
@@ -24,17 +24,19 @@
 
     <text class="contract-doc__commitment">{{ document.commitment }}</text>
 
-    <view v-if="signature" class="contract-doc__signatures">
+    <view v-if="signature || document.partyBSeal" class="contract-doc__signatures">
       <view class="contract-doc__sign">
         <text class="contract-doc__sign-label">甲方（签名）</text>
-        <image class="contract-doc__sign-image" :src="signature.memberSignature" mode="aspectFit" />
-        <text class="contract-doc__sign-meta">{{ signature.signerName }}</text>
+        <image v-if="signature" class="contract-doc__sign-image" :src="signature.memberSignature" mode="aspectFit" />
+        <text v-else class="contract-doc__sign-meta">待会员签署</text>
+        <text v-if="signature" class="contract-doc__sign-meta">{{ signature.signerName }}</text>
         <text class="contract-doc__sign-meta">{{ signedAtText }}</text>
       </view>
       <view class="contract-doc__sign">
         <text class="contract-doc__sign-label">乙方（签章）</text>
-        <image v-if="signature.partyBSignature" class="contract-doc__sign-image" :src="signature.partyBSignature" mode="aspectFit" />
-        <text class="contract-doc__sign-meta">{{ signature.partyBName }}</text>
+        <image v-if="signature?.partyBSignature" class="contract-doc__sign-image" :src="signature.partyBSignature" mode="aspectFit" />
+        <image v-if="document.partyBSeal" class="contract-doc__seal-image" :src="document.partyBSeal" mode="aspectFit" />
+        <text class="contract-doc__sign-meta">{{ partyBName }}</text>
         <text class="contract-doc__sign-meta">{{ signedAtText }}</text>
       </view>
     </view>
@@ -59,6 +61,8 @@ const groups = computed(() => [
 ])
 
 const signedAtText = computed(() => props.signature ? `签署于 ${formatDateTimeFull(props.signature.signedAt)}` : '')
+const partyBName = computed(() => props.signature?.partyBName
+  || props.document.partyB.find(row => row.label === '经营者名称')?.value || '')
 </script>
 
 <style lang="scss" scoped>
@@ -79,6 +83,7 @@ const signedAtText = computed(() => props.signature ? `签署于 ${formatDateTim
   &__sign { flex: 1; min-width: 0; padding: 20rpx; border-radius: 16rpx; background: #faf6f1; }
   &__sign-label { display: block; font-size: 23rpx; color: #8b7f74; }
   &__sign-image { display: block; width: 100%; height: 140rpx; margin: 10rpx 0; }
+  &__seal-image { display: block; width: 100%; height: 220rpx; margin: 10rpx 0; }
   &__sign-meta { display: block; font-size: 21rpx; line-height: 1.7; color: #8b7f74; overflow-wrap: anywhere; }
   &__digest { display: block; margin-top: 20rpx; font-size: 19rpx; line-height: 1.6; color: #b0a498; word-break: break-all; }
 }
diff --git a/packages/app/src/pages/admin/contract-settings.vue b/packages/app/src/pages/admin/contract-settings.vue
index 4d8c922..5bdd553 100644
--- a/packages/app/src/pages/admin/contract-settings.vue
+++ b/packages/app/src/pages/admin/contract-settings.vue
@@ -73,8 +73,13 @@
       </view>
 
       <view class="panel">
-        <view class="panel-heading"><text class="section-number">03</text><text class="section-title">经营者签名</text></view>
-        <text class="hint">签名会作为乙方签章出现在每份合同中，签署时自动加载。建议由经营者本人书写。</text>
+        <view class="panel-heading"><text class="section-number">03</text><text class="section-title">乙方合同专用章</text></view>
+        <text class="hint">已默认加载场馆合同专用章，签署、查看及导出合同均会展示。合同章随签署内容保存，已签合同不受后续修改影响。</text>
+        <view class="seal-preview">
+          <image v-if="config?.sealImage" :src="config.sealImage" mode="aspectFit" class="seal-image" />
+        </view>
+        <text class="field-label">经营者签名（选填）</text>
+        <text class="hint">可由经营者本人书写，与合同章一同展示。</text>
         <template v-if="signing">
           <SignaturePad ref="pad" :height="360" placeholder="请经营者本人手写签名" @change="onSignatureChange" />
           <view class="sign-actions">
@@ -273,6 +278,8 @@ button[disabled] { opacity: .42; }
 .segment .selected { background: #fffdf8; color: #4f6243; }
 .signature-preview { height: 200rpx; border-radius: 16rpx; background: #f5f4ec; display: flex; align-items: center; justify-content: center; margin-bottom: 20rpx; }
 .signature-image { width: 100%; height: 180rpx; }
+.seal-preview { display: flex; justify-content: center; margin-bottom: 24rpx; background: #fff; border-radius: 16rpx; }
+.seal-image { width: 300rpx; height: 300rpx; }
 .add-button { width: 100%; height: 84rpx; border: 1rpx dashed #bdc6ab; background: #f3f5eb; color: #74835f; }
 .sign-actions { display: flex; gap: 16rpx; margin-top: 20rpx; }
 .ghost-button { flex: 1; height: 80rpx; background: #eef0e6; color: #6d7a5d; }
diff --git a/packages/server/assets/contracts/party-b-seal.jpg b/packages/server/assets/contracts/party-b-seal.jpg
new file mode 100644
index 0000000..67741ce
Binary files /dev/null and b/packages/server/assets/contracts/party-b-seal.jpg differ
diff --git a/packages/server/src/contract/__tests__/contract.service.spec.ts b/packages/server/src/contract/__tests__/contract.service.spec.ts
index 70f9f08..e7ecd10 100644
--- a/packages/server/src/contract/__tests__/contract.service.spec.ts
+++ b/packages/server/src/contract/__tests__/contract.service.spec.ts
@@ -3,6 +3,7 @@ import { Decimal } from '@prisma/client/runtime/library'
 import { MembershipContractSource, MembershipContractStatus } from '@mp-pilates/shared'
 import { ContractService, decodeSignaturePng } from '../contract.service'
 import { buildContractDocument, hashContractDocument } from '../contract-template'
+import { DEFAULT_CONTRACT_SEAL } from '../contract-seal'
 
 const PNG = Buffer.concat([Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]), Buffer.alloc(800, 1)])
 const PNG_DATA_URI = `data:image/png;base64,${PNG.toString('base64')}`
@@ -249,7 +250,7 @@ describe('ContractService.sign', () => {
     source: MembershipContractSource.PURCHASE,
     terms: terms as never,
     partyA: { realName: '张三', phone: '13800000000', openid: 'openid-123456789' },
-    partyB: { ...party, premisesType: 'LEASED', leaseEndDate: null },
+    partyB: { ...party, premisesType: 'LEASED', leaseEndDate: null, sealImage: DEFAULT_CONTRACT_SEAL },
     cancelHoursLimit: 2,
   }))
   const dto = { contentSha256: expectedHash, signatureImage: PNG_DATA_URI, agreedTerms: true, confirmedHealth: true }
@@ -269,7 +270,7 @@ describe('ContractService.sign', () => {
 
   it('rejects signing until party B profile is complete', async () => {
     const { service, prisma } = buildService()
-    prisma.contractParty.findFirst.mockResolvedValue({ ...party, signatureImage: null })
+    prisma.contractParty.findFirst.mockResolvedValue({ ...party, businessName: '' })
     prisma.membershipContract.findUnique.mockResolvedValue(contract)
     await expect(service.sign('user-1', 'contract-1', dto, meta)).rejects.toBeInstanceOf(BadRequestException)
   })
@@ -286,11 +287,52 @@ describe('ContractService.sign', () => {
       contentSha256: expectedHash,
       signerIp: '1.2.3.4',
       partyBSignatureImage: PNG,
+      document: expect.objectContaining({ partyBSeal: DEFAULT_CONTRACT_SEAL }),
     })
     expect(update.data.signatureSha256).toMatch(/^[a-f0-9]{64}$/)
     expect(prisma.contractEvent.create).toHaveBeenCalledWith(expect.objectContaining({ data: expect.objectContaining({ action: 'SIGNED' }) }))
   })
 
+  it('shows the default seal before signing and allows signing without a handwritten party B signature', async () => {
+    const { service, prisma } = buildService()
+    prisma.contractParty.findFirst.mockResolvedValue({ ...party, signatureImage: null, signatureSha256: null })
+    prisma.membershipContract.findUnique.mockResolvedValue(contract)
+    prisma.membershipContract.updateMany.mockResolvedValue({ count: 1 })
+    const detail = await service.getDetail(contract.id, { id: 'user-1', isAdmin: false })
+    expect(detail.signable).toBe(true)
+    expect(detail.document.partyBSeal).toBe(DEFAULT_CONTRACT_SEAL)
+    const config = await service.getPartyConfig()
+    expect(config.sealImage).toBe(DEFAULT_CONTRACT_SEAL)
+    expect(config.missingFields).toEqual([])
+    await service.sign('user-1', contract.id, { ...dto, contentSha256: detail.contentSha256 }, meta)
+    expect(prisma.membershipContract.updateMany.mock.calls[0][0].data).toMatchObject({
+      partyBSignatureImage: null,
+      document: expect.objectContaining({ partyBSeal: DEFAULT_CONTRACT_SEAL }),
+    })
+  })
+
+  it('uses only the frozen document and seal for signed detail and PDF, including old contracts without a seal', async () => {
+    const { service, prisma, pdf } = buildService()
+    const document = buildContractDocument({
+      contractNo: contract.contractNo, source: MembershipContractSource.PURCHASE, terms: terms as never,
+      partyA: { realName: '张三', phone: '13800000000', openid: contract.user.openid },
+      partyB: { ...party, premisesType: 'LEASED', leaseEndDate: null, sealImage: DEFAULT_CONTRACT_SEAL },
+      cancelHoursLimit: 2,
+    })
+    for (const seal of [DEFAULT_CONTRACT_SEAL, undefined]) {
+      const snapshot = { ...document, partyBSeal: seal }
+      prisma.membershipContract.findUnique.mockResolvedValue({
+        ...contract, status: 'SIGNED', document: snapshot, signatureImage: PNG,
+        partyBSignatureImage: PNG, partyBName: '签署时的场馆', signedAt: new Date(), contentSha256: 'frozen-hash',
+      })
+      const detail = await service.getDetail(contract.id, { id: 'user-1', isAdmin: false })
+      expect(detail.document.partyBSeal).toBe(seal)
+      await service.exportPdf(contract.id, { id: 'user-1', isAdmin: false }, meta)
+      expect(pdf.render).toHaveBeenLastCalledWith(expect.objectContaining({ document: snapshot, partyBName: '签署时的场馆' }))
+    }
+    expect(prisma.contractParty.findFirst).not.toHaveBeenCalled()
+  })
+
   it('reports a concurrent signature as a conflict', async () => {
     const { service, prisma } = buildService()
     prisma.membershipContract.findUnique.mockResolvedValue(contract)
diff --git a/packages/server/src/contract/contract-pdf.service.ts b/packages/server/src/contract/contract-pdf.service.ts
index 46f2a89..70268e1 100644
--- a/packages/server/src/contract/contract-pdf.service.ts
+++ b/packages/server/src/contract/contract-pdf.service.ts
@@ -128,11 +128,16 @@ export class ContractPdfService {
   }
 
   private signatures(doc: PDFKit.PDFDocument, input: ContractPdfInput, width: number) {
-    const blockHeight = 150
-    if (doc.y + blockHeight > doc.page.height - doc.page.margins.bottom) doc.addPage()
-    doc.moveDown(1.2)
-    const top = doc.y
     const column = width / 2
+    const seal = input.document.partyBSeal
+    const mediaHeight = (input.partyBSignature ? 70 : 0) + (seal ? 124 : 0)
+    const nameOffset = Math.max(94, 18 + mediaHeight + 6)
+    doc.fontSize(9)
+    const nameHeight = doc.heightOfString(input.partyBName, { width: column - 12 })
+    const blockHeight = nameOffset + nameHeight + 30
+    doc.moveDown(1.2)
+    if (doc.y + blockHeight > doc.page.height - doc.page.margins.bottom) doc.addPage()
+    const top = doc.y
     const signedAt = formatChinaDateTime(input.signedAt)
 
     doc.fontSize(10).fillColor(TEXT_COLOR)
@@ -146,9 +151,10 @@ export class ContractPdfService {
     doc.fontSize(10).fillColor(TEXT_COLOR)
     doc.text('乙方（签章）：', right, top)
     if (input.partyBSignature) doc.image(input.partyBSignature, right, top + 18, { fit: [column - 24, 70] })
+    if (seal) doc.image(seal, right, top + 18 + (input.partyBSignature ? 70 : 0), { fit: [column - 24, 118], align: 'center' })
     doc.fontSize(9).fillColor(MUTED_COLOR)
-    doc.text(input.partyBName, right, top + 94, { width: column })
-    doc.text(`签署时间：${signedAt}`, right, top + 110)
+    doc.text(input.partyBName, right, top + nameOffset, { width: column - 12 })
+    doc.text(`签署时间：${signedAt}`, right, top + nameOffset + nameHeight + 6)
     doc.x = PAGE_MARGIN
     doc.y = top + blockHeight
   }
diff --git a/packages/server/src/contract/contract-seal.ts b/packages/server/src/contract/contract-seal.ts
new file mode 100644
index 0000000..47e89d2
--- /dev/null
+++ b/packages/server/src/contract/contract-seal.ts
@@ -0,0 +1,7 @@
+import { readFileSync } from 'fs'
+import { join } from 'path'
+
+/** 场馆提供的合同专用章；签署后只读取合同内的快照。 */
+export const DEFAULT_CONTRACT_SEAL = `data:image/jpeg;base64,${readFileSync(
+  join(__dirname, '..', '..', 'assets', 'contracts', 'party-b-seal.jpg'),
+).toString('base64')}`
diff --git a/packages/server/src/contract/contract-template.ts b/packages/server/src/contract/contract-template.ts
index 60842c7..83ccc87 100644
--- a/packages/server/src/contract/contract-template.ts
+++ b/packages/server/src/contract/contract-template.ts
@@ -53,6 +53,7 @@ export interface ContractPartyBInput {
   premisesType: ContractPremisesType
   leaseEndDate: string | null
   standardLessonPrice: number
+  sealImage?: string
 }
 
 export interface ContractRenderInput {
@@ -397,6 +398,7 @@ export function buildContractDocument(input: ContractRenderInput): ContractDocum
     cardRows: buildCardRows(input),
     sections: buildSections(input),
     commitment: '甲方承诺：本人确认所填写的姓名、联系方式真实有效，已如实告知身体健康状况，已仔细阅读并理解本合同全部条款（特别是加粗条款），自愿签署本合同。',
+    ...(input.partyB.sealImage ? { partyBSeal: input.partyB.sealImage } : {}),
   }
 }
 
diff --git a/packages/server/src/contract/contract.service.ts b/packages/server/src/contract/contract.service.ts
index 879b2a3..7204266 100644
--- a/packages/server/src/contract/contract.service.ts
+++ b/packages/server/src/contract/contract.service.ts
@@ -29,6 +29,7 @@ import {
 import { PrismaService } from '../prisma/prisma.service'
 import { StudioService } from '../studio/studio.service'
 import { ContractPdfService } from './contract-pdf.service'
+import { DEFAULT_CONTRACT_SEAL } from './contract-seal'
 import {
   CONTRACT_TEMPLATE_VERSION,
   buildContractDocument,
@@ -487,6 +488,7 @@ export class ContractService {
       standardLessonPrice: input.standardLessonPrice,
       standardLessonPriceConfigured: party.standardLessonPrice > 0,
       signatureImage: toDataUri(party.signatureImage),
+      sealImage: DEFAULT_CONTRACT_SEAL,
       signatureUpdatedAt: party.signatureUpdatedAt?.toISOString() ?? null,
       missingFields: this.missingFields(party, input),
     }
@@ -610,6 +612,7 @@ export class ContractService {
       premisesType: party.premisesType === 'OWNED' ? 'OWNED' : 'LEASED',
       leaseEndDate: party.leaseEndDate?.toISOString() ?? null,
       standardLessonPrice,
+      sealImage: DEFAULT_CONTRACT_SEAL,
     }
   }
 
@@ -621,7 +624,6 @@ export class ContractService {
     if (!party.phone.trim()) missing.push('联系电话')
     if (!party.address.trim()) missing.push('经营场所')
     if (input.standardLessonPrice <= 0) missing.push('单节标准课价')
-    if (!party.signatureImage) missing.push('经营者签名')
     return missing
   }
 
diff --git a/packages/shared/src/types/contract.ts b/packages/shared/src/types/contract.ts
index 63e1fdb..3da6154 100644
--- a/packages/shared/src/types/contract.ts
+++ b/packages/shared/src/types/contract.ts
@@ -30,6 +30,8 @@ export interface ContractDocument {
   readonly cardRows: readonly ContractRow[]
   readonly sections: readonly ContractSection[]
   readonly commitment: string
+  /** 乙方合同章图片，随正文及摘要冻结；旧合同可能没有。 */
+  readonly partyBSeal?: string
 }
 
 export interface ContractSignatureInfo {
@@ -106,6 +108,7 @@ export interface ContractPartyConfig {
   readonly standardLessonPrice: number
   readonly standardLessonPriceConfigured: boolean
   readonly signatureImage: string | null
+  readonly sealImage: string
   readonly signatureUpdatedAt: string | null
   readonly missingFields: readonly string[]
 }