diff --git a/submission/api.py b/submission/api.py
index 9dd357f..35a1a4e 100644
--- a/submission/api.py
+++ b/submission/api.py
@@ -20,6 +20,7 @@ from django.db.models import (
     Q,
     Subquery,
 )
+from django.utils import timezone
 from account.decorators import admin_required
 from prompt.models import Conversation, Message
 from .classifier import classify_conversation_messages
@@ -44,6 +45,7 @@ from .schemas import (
     SubmissionIn,
     SubmissionOut,
     RatingScoreIn,
+    RandomRatingOut,
     TaskStatsOut,
     TopViewedItem,
     UserTag,
@@ -288,6 +290,37 @@ def list_by_user_task(request, user_id: int, task_id: int):
     )
 
 
+@router.get("/random-for-rating/", response=Optional[RandomRatingOut])
+@login_required
+def get_random_for_rating(request, exclude_id: Optional[UUID] = None):
+    """
+    随机返回一个待打分的其他同学的提交（用于AI生成期间的随手打分弹窗）
+    """
+    if request.user.role == RoleChoices.NORMAL:
+        today_start = timezone.now().replace(
+            hour=0, minute=0, second=0, microsecond=0
+        )
+        today_end = today_start + timezone.timedelta(days=1)
+        rating_count = Rating.objects.filter(
+            user=request.user, created__range=(today_start, today_end)
+        ).count()
+        if rating_count >= 30:
+            return None
+
+    candidates = (
+        Submission.objects.select_related("task", "user")
+        .exclude(user=request.user)
+        .exclude(ratings__user=request.user)
+    )
+    if exclude_id:
+        candidates = candidates.exclude(pk=exclude_id)
+
+    pending = candidates.annotate(rating_count=Count("ratings")).filter(
+        rating_count__lt=5
+    )
+    return pending.order_by("?").first() or candidates.order_by("?").first()
+
+
 @router.delete("/flags")
 @login_required
 def clear_all_flags(request):
diff --git a/submission/schemas.py b/submission/schemas.py
index 13f60cd..dab2e87 100644
--- a/submission/schemas.py
+++ b/submission/schemas.py
@@ -296,3 +296,34 @@ class PromptRoundOut(Schema):
     html: Optional[str] = None
     css: Optional[str] = None
     js: Optional[str] = None
+
+
+class RandomRatingOut(Schema):
+    submission_id: UUID
+    username: str
+    task_title: str
+    task_display: int
+    task_type: Literal["tutorial", "challenge"]
+    html: Optional[str] = None
+    css: Optional[str] = None
+    js: Optional[str] = None
+
+    @staticmethod
+    def resolve_submission_id(obj):
+        return obj.id
+
+    @staticmethod
+    def resolve_username(obj):
+        return obj.user.username
+
+    @staticmethod
+    def resolve_task_title(obj):
+        return obj.task.title
+
+    @staticmethod
+    def resolve_task_display(obj):
+        return obj.task.display
+
+    @staticmethod
+    def resolve_task_type(obj):
+        return obj.task.task_type
diff --git a/submission/tests.py b/submission/tests.py
index 6faf14e..b09f9b7 100644
--- a/submission/tests.py
+++ b/submission/tests.py
@@ -10,7 +10,7 @@ from account.models import RoleChoices
 from prompt.models import Conversation, Message
 from task.models import Task
 
-from .models import Award, Submission, SubmissionAward
+from .models import Award, Rating, Submission, SubmissionAward
 
 User = get_user_model()
 
@@ -533,3 +533,72 @@ class GradebookApiTest(TestCase):
         self.assertEqual(rows[1][2], "alice")
         self.assertEqual(rows[1][4], "4")
         self.assertEqual(rows[1][7], "4")
+
+
+class RandomForRatingApiTest(TestCase):
+    def setUp(self):
+        self.viewer = _make_user("viewer")
+        self.author = _make_user("author")
+        self.task = _make_task()
+
+    def _submission(self, user, html="<div>work</div>"):
+        return Submission.objects.create(
+            user=user, task=self.task, html=html, css="", js=""
+        )
+
+    def test_excludes_own_and_already_rated_submissions(self):
+        self._submission(self.viewer)  # 自己的提交，应排除
+        rated = self._submission(self.author)
+        Rating.objects.create(user=self.viewer, submission=rated, score=4)
+        eligible = self._submission(self.author)
+
+        self.client.force_login(self.viewer)
+        resp = self.client.get("/api/submission/random-for-rating/")
+
+        self.assertEqual(resp.status_code, 200)
+        data = resp.json()
+        self.assertIsNotNone(data)
+        self.assertEqual(data["submission_id"], str(eligible.id))
+        self.assertEqual(data["username"], "author")
+        self.assertEqual(data["task_title"], self.task.title)
+        self.assertEqual(data["task_display"], self.task.display)
+        self.assertEqual(data["task_type"], "challenge")
+
+    def test_prefers_submission_with_fewer_than_five_ratings(self):
+        raters = [_make_user(f"rater{i}") for i in range(5)]
+        many_ratings = self._submission(self.author, html="<div>many</div>")
+        for rater in raters:
+            Rating.objects.create(user=rater, submission=many_ratings, score=3)
+        few_ratings = self._submission(self.author, html="<div>few</div>")
+        for rater in raters[:2]:
+            Rating.objects.create(user=rater, submission=few_ratings, score=3)
+
+        self.client.force_login(self.viewer)
+        resp = self.client.get("/api/submission/random-for-rating/")
+
+        self.assertEqual(resp.status_code, 200)
+        data = resp.json()
+        self.assertEqual(data["submission_id"], str(few_ratings.id))
+
+    def test_exclude_id_param_excludes_given_submission(self):
+        only = self._submission(self.author)
+
+        self.client.force_login(self.viewer)
+        resp = self.client.get(
+            f"/api/submission/random-for-rating/?exclude_id={only.id}"
+        )
+
+        self.assertEqual(resp.status_code, 200)
+        self.assertIsNone(resp.json())
+
+    def test_normal_user_reaching_daily_cap_returns_none(self):
+        self._submission(self.author, html="<div>extra</div>")
+        for i in range(30):
+            target = self._submission(self.author, html=f"<div>{i}</div>")
+            Rating.objects.create(user=self.viewer, submission=target, score=3)
+
+        self.client.force_login(self.viewer)
+        resp = self.client.get("/api/submission/random-for-rating/")
+
+        self.assertEqual(resp.status_code, 200)
+        self.assertIsNone(resp.json())