diff --git a/backend/src/main/java/com/designhub/service/AnalyticsService.java b/backend/src/main/java/com/designhub/service/AnalyticsService.java
index 374b2ff..a19cd25 100644
--- a/backend/src/main/java/com/designhub/service/AnalyticsService.java
+++ b/backend/src/main/java/com/designhub/service/AnalyticsService.java
@@ -1323,13 +1323,14 @@ public class AnalyticsService {
                 .build();
         }
         
-        // 获取时间范围内的已完成任务
+        // 获取时间范围内的已完成任务（按完成时间查询）
         List<Task> completedTasks = taskMapper.selectList(
             new LambdaQueryWrapper<Task>()
                 .eq(Task::getReceiverId, userId)
                 .eq(Task::getStatus, "completed")
-                .ge(Task::getCreateTime, startTime)
-                .le(Task::getCreateTime, endTime)
+                .isNotNull(Task::getActualEndTime)
+                .ge(Task::getActualEndTime, startTime)
+                .le(Task::getActualEndTime, endTime)
         );
         
         // 获取扣分比例配置