diff --git a/src/server/routes/mileage/trend.ts b/src/server/routes/mileage/trend.ts
index dde16ab..b757fc0 100644
--- a/src/server/routes/mileage/trend.ts
+++ b/src/server/routes/mileage/trend.ts
@@ -19,8 +19,10 @@ app.get('/', async (c) => {
       if (plates.length === 0) return c.json([]);
     }
 
+    // 单车日里程负值视为脏数据（里程表回滚 / 换 GPS 设备），不纳入统计
     let sql = `
-      SELECT DATE_FORMAT(stat_date, '%m-%d') as date, SUM(daily_km) as mileage
+      SELECT DATE_FORMAT(stat_date, '%m-%d') as date,
+             SUM(IF(daily_km < 0, 0, daily_km)) as mileage
       FROM v_vehicle_daily_stats
       WHERE stat_date >= DATE_SUB(CURDATE(), INTERVAL ? DAY) AND stat_date < CURDATE()
     `;