diff --git a/apps/backend/src/services/worker-platform/worker-acceptance-service.ts b/apps/backend/src/services/worker-platform/worker-acceptance-service.ts
index e5de93fb..25e4e1a3 100644
--- a/apps/backend/src/services/worker-platform/worker-acceptance-service.ts
+++ b/apps/backend/src/services/worker-platform/worker-acceptance-service.ts
@@ -801,22 +801,29 @@ async function supplementWorkerAcceptedSharingEvidence(
   return { share: mapWorkOrderShare(updated || sharingShare) }
 }
 
+type WorkerTargetShareLike = { id: number; status: string }
+
+export type WorkerTargetShareSelection<T> = {
+  share: T | null
+  error: 'required' | 'not_found' | null
+}
+
 /**
  * 定位本次操作要处理的份额：
  * - 传了 shareId：必须是本人该工单下的有效份额（否则 not_found）
  * - 没传且只有 1 条：直接用
- * - 没传且有多条：要求前端明确指定（required）
+ * - 没传且有多条：优先唯一一条「进行中（joined）」份额；仍有多条才要求前端指定（required）
  * - 没有任何份额：返回空（走整单逻辑）
+ *
+ * 多条时优先 joined 是因为 submitted / accepted 的份额已经不能再提交验收：
+ * 第一份提交后只剩第二份待提交时，前端不传 shareId 也应该能直接定位到它。
  */
-async function resolveWorkerTargetShare(
-  workOrderId: number,
-  workerId: number | string,
-  payload: JsonObject,
-): Promise<{ share: WorkOrderShareRow | null; error: 'required' | 'not_found' | null }> {
-  const requested = Number(payload.shareId ?? payload.workOrderShareId ?? 0)
-  const shares = await listWorkOrderSharesByWorkerInOrder(workOrderId, workerId)
-  if (Number.isFinite(requested) && requested > 0) {
-    const found = shares.find((share) => Number(share.id) === requested) || null
+export function chooseWorkerTargetShare<T extends WorkerTargetShareLike>(
+  shares: T[],
+  requestedShareId: number,
+): WorkerTargetShareSelection<T> {
+  if (Number.isFinite(requestedShareId) && requestedShareId > 0) {
+    const found = shares.find((share) => Number(share.id) === requestedShareId) || null
     return { share: found, error: found ? null : 'not_found' }
   }
   if (shares.length === 0) {
@@ -825,9 +832,23 @@ async function resolveWorkerTargetShare(
   if (shares.length === 1) {
     return { share: shares[0] ?? null, error: null }
   }
+  const pendingShares = shares.filter((share) => String(share.status) === 'joined')
+  if (pendingShares.length === 1) {
+    return { share: pendingShares[0] ?? null, error: null }
+  }
   return { share: null, error: 'required' }
 }
 
+async function resolveWorkerTargetShare(
+  workOrderId: number,
+  workerId: number | string,
+  payload: JsonObject,
+): Promise<WorkerTargetShareSelection<WorkOrderShareRow>> {
+  const requested = Number(payload.shareId ?? payload.workOrderShareId ?? 0)
+  const shares = await listWorkOrderSharesByWorkerInOrder(workOrderId, workerId)
+  return chooseWorkerTargetShare(shares, requested)
+}
+
 const ACCEPTANCE_VIDEO_SCENE = 'worker-acceptance-video'
 const ACCEPTANCE_VIDEO_CONTENT_TYPES = new Set(['video/mp4', 'video/webm'])
 
diff --git a/apps/backend/src/services/worker-platform/worker-acceptance-target-share.test.ts b/apps/backend/src/services/worker-platform/worker-acceptance-target-share.test.ts
new file mode 100644
index 00000000..e9b082fd
--- /dev/null
+++ b/apps/backend/src/services/worker-platform/worker-acceptance-target-share.test.ts
@@ -0,0 +1,51 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import { chooseWorkerTargetShare } from './worker-acceptance-service.js'
+
+const submitted = { id: 11, status: 'submitted' }
+const joined = { id: 12, status: 'joined' }
+const accepted = { id: 13, status: 'accepted' }
+
+test('份额选择：指定 shareId 命中本人份额', () => {
+  const result = chooseWorkerTargetShare([submitted, joined], 12)
+  assert.equal(result.error, null)
+  assert.equal(result.share?.id, 12)
+})
+
+test('份额选择：指定了不属于自己的 shareId 返回 not_found', () => {
+  const result = chooseWorkerTargetShare([submitted, joined], 99)
+  assert.equal(result.error, 'not_found')
+  assert.equal(result.share, null)
+})
+
+test('份额选择：没有任何份额时走整单逻辑', () => {
+  const result = chooseWorkerTargetShare([], 0)
+  assert.equal(result.error, null)
+  assert.equal(result.share, null)
+})
+
+test('份额选择：只有一条份额时直接使用，不要求 shareId', () => {
+  const result = chooseWorkerTargetShare([joined], 0)
+  assert.equal(result.error, null)
+  assert.equal(result.share?.id, joined.id)
+})
+
+test('份额选择：多条中只剩一条 joined 时自动选中，不再要求 shareId', () => {
+  const result = chooseWorkerTargetShare([submitted, joined, accepted], 0)
+  assert.equal(result.error, null)
+  assert.equal(result.share?.id, joined.id)
+})
+
+test('份额选择：多条 joined 时仍要求显式指定', () => {
+  const secondJoined = { id: 14, status: 'joined' }
+  const result = chooseWorkerTargetShare([joined, secondJoined, submitted], 0)
+  assert.equal(result.error, 'required')
+  assert.equal(result.share, null)
+})
+
+test('份额选择：全部已提交/已验收时不能自动选中', () => {
+  const result = chooseWorkerTargetShare([submitted, accepted], 0)
+  assert.equal(result.error, 'required')
+  assert.equal(result.share, null)
+})
diff --git a/apps/frontend/src/pages/worker/WorkerOrdersPage.tsx b/apps/frontend/src/pages/worker/WorkerOrdersPage.tsx
index f3aac03a..ee6d022f 100644
--- a/apps/frontend/src/pages/worker/WorkerOrdersPage.tsx
+++ b/apps/frontend/src/pages/worker/WorkerOrdersPage.tsx
@@ -323,8 +323,12 @@ export default function WorkerOrdersPage() {
   }
 
   function openAcceptanceModal(order: WorkOrder) {
-    markOrderAsRead(order)
     const shares = getOrderShares(order)
+    if (shares.length === 0) {
+      message.warning('未找到可验收的拼单份额，请刷新后重试')
+      return
+    }
+    markOrderAsRead(order)
     if (shares.length > 1) {
       setPickedShareId(shares[0]?.shareId || 0)
       setSharePicker({ order, action: 'accept' })
@@ -487,6 +491,10 @@ export default function WorkerOrdersPage() {
 
   async function submitAcceptance(values: AcceptanceFormValues) {
     if (!editingOrder) return
+    if (getOrderShares(editingOrder).length > 1 && !editingShareId) {
+      message.warning('请先选择要验收的拼单份额')
+      return
+    }
     const isAcceptedEvidenceSupplement = canSupplementAcceptedEvidence(editingOrder)
     if (isAcceptedEvidenceSupplement) {
       if (acceptanceFiles.length === 0 && !acceptanceVideoDirty) {
@@ -552,6 +560,10 @@ export default function WorkerOrdersPage() {
 
   async function saveAcceptanceImages(values: AcceptanceFormValues) {
     if (!editingOrder) return
+    if (getOrderShares(editingOrder).length > 1 && !editingShareId) {
+      message.warning('请先选择要操作的拼单份额')
+      return
+    }
     if (hasSubmittedAcceptance(editingOrder) && acceptanceFiles.length === 0 && !acceptanceVideo) {
       message.error('请至少保留一张验收图片或一段验收视频')
       return