diff --git a/backend/src/main/java/com/designhub/service/TaskService.java b/backend/src/main/java/com/designhub/service/TaskService.java
index 96792b5..fba4c62 100644
--- a/backend/src/main/java/com/designhub/service/TaskService.java
+++ b/backend/src/main/java/com/designhub/service/TaskService.java
@@ -2466,15 +2466,17 @@ public class TaskService {
                 taskId, task.getPublisherDeptId(), scoreToRefund);
         }
         
-        // 更新任务状态为草稿
-        task.setStatus("draft");
-        task.setApprovalStatus(null);  // 清除审批状态
-        task.setCurrentApproverId(null);
-        task.setCurrentApproverRole(null);
-        task.setAuditStatus("draft");  // 重置审核状态
-        task.setUpdateTime(LocalDateTime.now());
-        
-        taskMapper.updateById(task);
+        // 更新任务状态为草稿（使用 LambdaUpdateWrapper 确保 null 值也能更新）
+        taskMapper.update(null, 
+            new LambdaUpdateWrapper<Task>()
+                .eq(Task::getId, taskId)
+                .set(Task::getStatus, "draft")
+                .set(Task::getApprovalStatus, null)  // 清除审批状态
+                .set(Task::getCurrentApproverId, null)
+                .set(Task::getCurrentApproverRole, null)
+                .set(Task::getAuditStatus, "draft")  // 重置审核状态
+                .set(Task::getUpdateTime, LocalDateTime.now())
+        );
         
         // 如果是流水线任务，也需要重置子任务状态
         if (task.getIsPipeline() != null && task.getIsPipeline() == 1) {