diff --git a/backend/app/api/auth.py b/backend/app/api/auth.py
index 6a787dd..006032c 100644
--- a/backend/app/api/auth.py
+++ b/backend/app/api/auth.py
@@ -7,13 +7,30 @@ from app.core.auth import hash_password, verify_password, create_access_token
 from app.core.deps import get_current_user
 from app.db.database import get_db
 from app.db.models import ClassMembership, User
-from app.schemas.auth import LoginRequest, RegisterRequest, ChangePasswordRequest
+from app.schemas.auth import (
+    ChangePasswordRequest,
+    InviteCodeClassPreview,
+    LoginRequest,
+    RegisterRequest,
+)
 from app.schemas.user import TokenResponse, UserOut, build_user_out
-from app.services.member_activation_service import validate_registration
+from app.services.member_activation_service import get_class_by_invite_code, validate_registration
 
 router = APIRouter(prefix="/api/auth", tags=["auth"])
 
 
+@router.get("/invite-code/{invite_code}", response_model=InviteCodeClassPreview)
+async def preview_invite_code_class(invite_code: str, db: AsyncSession = Depends(get_db)):
+    class_ = await get_class_by_invite_code(db, invite_code.strip().upper())
+    if class_ is None:
+        raise HTTPException(status_code=404, detail="邀请码无效")
+    return InviteCodeClassPreview(
+        id=class_.id,
+        name=class_.name,
+        cohort_year=class_.cohort_year,
+    )
+
+
 @router.post("/activate")
 async def activate_account(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
     # 1. Check if email is already in use
diff --git a/backend/app/schemas/auth.py b/backend/app/schemas/auth.py
index 04d4c5f..df02d63 100644
--- a/backend/app/schemas/auth.py
+++ b/backend/app/schemas/auth.py
@@ -16,3 +16,9 @@ class RegisterRequest(BaseModel):
 class ChangePasswordRequest(BaseModel):
     old_password: str
     new_password: str
+
+
+class InviteCodeClassPreview(BaseModel):
+    id: int
+    name: str
+    cohort_year: int
diff --git a/backend/app/services/member_activation_service.py b/backend/app/services/member_activation_service.py
index da9bfa5..155da88 100644
--- a/backend/app/services/member_activation_service.py
+++ b/backend/app/services/member_activation_service.py
@@ -173,6 +173,11 @@ async def validate_registration(
     return user, class_.id
 
 
+async def get_class_by_invite_code(db: AsyncSession, invite_code: str) -> Class_ | None:
+    result = await db.execute(select(Class_).where(Class_.invite_code == invite_code))
+    return result.scalar_one_or_none()
+
+
 async def delete_inactive_member(db: AsyncSession, class_id: int, user_id: int) -> bool:
     result = await db.execute(
         select(User)
diff --git a/frontend/src/app/activate/page.tsx b/frontend/src/app/activate/page.tsx
index 900dbdf..b456032 100644
--- a/frontend/src/app/activate/page.tsx
+++ b/frontend/src/app/activate/page.tsx
@@ -6,16 +6,25 @@ import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card";
-import { getErrorMessage, postAPI } from "@/lib/api";
+import { fetchAPI, getErrorMessage, postAPI } from "@/lib/api";
 import Link from "next/link";
 import type { LoginResponse } from "@/lib/types";
 
+type InviteCodeClassPreview = {
+  id: number;
+  name: string;
+  cohort_year: number;
+};
+
 export default function ActivatePage() {
   const [inviteCode, setInviteCode] = useState("");
   const [studentId, setStudentId] = useState("");
   const [email, setEmail] = useState("");
   const [password, setPassword] = useState("");
   const [confirmPassword, setConfirmPassword] = useState("");
+  const [classPreview, setClassPreview] = useState<InviteCodeClassPreview | null>(null);
+  const [classLookupLoading, setClassLookupLoading] = useState(false);
+  const [classLookupError, setClassLookupError] = useState("");
   const [error, setError] = useState("");
   const [loading, setLoading] = useState(false);
   const router = useRouter();
@@ -28,6 +37,32 @@ export default function ActivatePage() {
     }
   }, [searchParams]);
 
+  useEffect(() => {
+    const normalizedCode = inviteCode.trim().toUpperCase();
+    if (!normalizedCode) {
+      setClassPreview(null);
+      setClassLookupError("");
+      setClassLookupLoading(false);
+      return;
+    }
+
+    const timer = window.setTimeout(async () => {
+      setClassLookupLoading(true);
+      setClassLookupError("");
+      try {
+        const res = await fetchAPI<InviteCodeClassPreview>(`/api/auth/invite-code/${encodeURIComponent(normalizedCode)}`);
+        setClassPreview(res);
+      } catch {
+        setClassPreview(null);
+        setClassLookupError("未找到对应班级，请确认邀请码是否正确");
+      } finally {
+        setClassLookupLoading(false);
+      }
+    }, 300);
+
+    return () => window.clearTimeout(timer);
+  }, [inviteCode]);
+
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
     setError("");
@@ -98,6 +133,17 @@ export default function ActivatePage() {
                 onChange={(e) => setInviteCode(e.target.value.toUpperCase())}
                 required
               />
+              {classLookupLoading && (
+                <p className="text-xs text-[#9a7b68]">正在识别班级...</p>
+              )}
+              {!classLookupLoading && classPreview && (
+                <div className="rounded-2xl border border-[#d8c1a1] bg-[#fff4e3] px-3 py-2 text-sm text-[#6f4b32]">
+                  班级确认：{classPreview.name}
+                </div>
+              )}
+              {!classLookupLoading && classLookupError && (
+                <p className="text-xs text-red-600">{classLookupError}</p>
+              )}
             </div>
             <div className="space-y-2">
               <Label htmlFor="studentId">学号</Label>