diff --git a/backend/community/admin.py b/backend/community/admin.py
index 3dc2d1f..1952105 100644
--- a/backend/community/admin.py
+++ b/backend/community/admin.py
@@ -202,16 +202,16 @@ class TopicAdmin(OrderableAdminMixin, ModelAdmin):
     inlines = [TopicMediaInline, ReplyInline]
     actions = ['reset_ordering']
 
-    @admin.action(description="重置排序 (按ID顺序)")
+    @admin.action(description="重置排序 (按发布时间倒序)")
     def reset_ordering(self, request, queryset):
         """
-        将所有帖子按ID顺序重新分配order值
+        将所有帖子按时间倒序重新分配order值（order = -id）
         """
-        all_objects = Topic.objects.all().order_by('id')
-        for index, obj in enumerate(all_objects, start=1):
-            obj.order = index
+        all_objects = Topic.objects.all().order_by('-id')
+        for obj in all_objects:
+            obj.order = -obj.id
             obj.save(update_fields=['order'])
-        self.message_user(request, f"成功重置了 {all_objects.count()} 个帖子的排序权重。")
+        self.message_user(request, f"成功重置了 {all_objects.count()} 个帖子的排序权重（新帖子在前）。")
     
     fieldsets = (
         ('帖子内容', {
diff --git a/backend/community/models.py b/backend/community/models.py
index f08d356..b2cc2af 100644
--- a/backend/community/models.py
+++ b/backend/community/models.py
@@ -145,8 +145,9 @@ class Topic(models.Model):
         is_new = self.pk is None
         super().save(*args, **kwargs)
         if is_new and getattr(self, 'order', 0) == 0:
-            Topic.objects.filter(pk=self.pk).update(order=self.pk)
-            self.order = self.pk
+            # 默认使用 -id 作为排序值，确保新帖子默认排在前面（order越小越靠前）
+            Topic.objects.filter(pk=self.pk).update(order=-self.pk)
+            self.order = -self.pk
 
     def __str__(self):
         return self.title