diff --git a/src/modules/mileage/MonitoringView.tsx b/src/modules/mileage/MonitoringView.tsx
index 9ba4af9..258aeee 100644
--- a/src/modules/mileage/MonitoringView.tsx
+++ b/src/modules/mileage/MonitoringView.tsx
@@ -201,6 +201,14 @@ export default function MonitoringView() {
     loadFirstPage();
   }, [loadFirstPage]);
 
+  // 区域级联：plate 选项收窄后，剔除已选但已不属于该区域的车牌
+  useEffect(() => {
+    if (filterPlates.length === 0) return;
+    const valid = new Set(filterOptions.plates);
+    const next = filterPlates.filter(p => valid.has(p));
+    if (next.length !== filterPlates.length) setFilterPlates(next);
+  }, [filterOptions.plates, filterPlates]);
+
   // 下载当前筛选结果为 xlsx
   const handleDownload = useCallback(async () => {
     if (exporting) return;
diff --git a/src/server/routes/mileage/monitoring.ts b/src/server/routes/mileage/monitoring.ts
index 1947b20..d64b763 100644
--- a/src/server/routes/mileage/monitoring.ts
+++ b/src/server/routes/mileage/monitoring.ts
@@ -100,6 +100,12 @@ app.get('/', async (c) => {
     filters = buildDateFilters(allVehicles); // 重算筛选选项以匹配权限范围
   }
 
+  // 区域级联：选中运营区域时，下游筛选选项（车牌等）只展示该区域车辆
+  if (filterParams.region) {
+    const regionScope = allVehicles.filter(v => v.region === filterParams.region);
+    filters = buildDateFilters(regionScope);
+  }
+
   const filtered = applyFilters(allVehicles, filterParams);
 
   const stats = {