diff --git a/backend/app/routers/websites.py b/backend/app/routers/websites.py
index 9a3fabb..64913ce 100644
--- a/backend/app/routers/websites.py
+++ b/backend/app/routers/websites.py
@@ -189,12 +189,6 @@ def _numeric_group_id(value: str | None) -> int | None:
         return None
 
 
-def _build_rate_priority_map(db: Session, upstream_ids: set[int]) -> dict[str, int]:
-    """根据上游分组倍率构建 group_id → priority 映射。
-    
-    委托给 website_sync.build_rate_priority_map 避免逻辑重复。
-    """
-    return build_rate_priority_map(db, upstream_ids)
 
 
 @router.get("/api/websites", response_model=List[WebsiteResponse])
diff --git a/backend/app/services/website_sync.py b/backend/app/services/website_sync.py
index a066c4a..fef13de 100644
--- a/backend/app/services/website_sync.py
+++ b/backend/app/services/website_sync.py
@@ -220,6 +220,17 @@ def _snapshot_group_rate(group: dict) -> float:
         return 1.0
 
 
+def _strict_snapshot_group_rate(group: dict) -> float | None:
+    """从快照分组数据中严格提取倍率，若缺失或非数值则返回 None。"""
+    raw = group.get("rate") or group.get("default_rate") or group.get("rate_multiplier")
+    if raw is None or raw == "":
+        return None
+    try:
+        return float(raw)
+    except (TypeError, ValueError):
+        return None
+
+
 def build_rate_priority_map(db: Session, upstream_ids: set[int]) -> dict[str, int]:
     """根据上游分组倍率构建 f"{upstream_id}:{group_id}" → priority 映射。
 
@@ -465,8 +476,9 @@ def build_target_group_priority_map(
             groups = rate_maps.get(upstream_id) or {}
             g = groups.get(group_id)
             if isinstance(g, dict):
-                rate = _snapshot_group_rate(g)
-                rated_sources.append(((upstream_id, group_id), rate))
+                rate = _strict_snapshot_group_rate(g)
+                if rate is not None:
+                    rated_sources.append(((upstream_id, group_id), rate))
 
         if not rated_sources:
             continue
diff --git a/backend/test_priority_algorithm_correction.py b/backend/test_priority_algorithm_correction.py
index 0006857..e2076d0 100644
--- a/backend/test_priority_algorithm_correction.py
+++ b/backend/test_priority_algorithm_correction.py
@@ -62,6 +62,7 @@ def test_target_group_priority_calculation(db_session):
         "G3": 0.07,
         "G4": 0.08,
         "G5": 0.05,  # identical rate as G1
+        "G6": "invalid_rate",  # invalid rate
     })
 
     target_group_sources = {
@@ -71,6 +72,8 @@ def test_target_group_priority_calculation(db_session):
             (u1.id, "G3"),
             (u1.id, "G4"),
             (u1.id, "G5"),
+            (u1.id, "G6"),
+            (u1.id, "G7"),  # non-existent G7
         ],
         "TG2": [
             (u1.id, "G2"),  # rates 0.065 -> priority 1
@@ -90,6 +93,8 @@ def test_target_group_priority_calculation(db_session):
     assert priority_map[("TG1", u1.id, "G2")] == 11
     assert priority_map[("TG1", u1.id, "G3")] == 21
     assert priority_map[("TG1", u1.id, "G4")] == 31
+    assert ("TG1", u1.id, "G6") not in priority_map
+    assert ("TG1", u1.id, "G7") not in priority_map
 
     # Assert priority values in TG2 (starts from 1 independently)
     # 0.065 -> rank 0 -> priority 1