diff --git a/backend/app/services/order_service.py b/backend/app/services/order_service.py
index d7d0c97..42f4bbe 100644
--- a/backend/app/services/order_service.py
+++ b/backend/app/services/order_service.py
@@ -131,10 +131,11 @@ class OrderService:
 
             try:
                 result = pricing_engine.calculate_for_order_item(rule, user_inputs, product_attrs)
-                # 不覆盖前端传入的 cost_price，只填充快照字段用于展示
                 item_copy = dict(item)
-                # 填充快照字段
+                # 使用定价引擎计算的 cost_price（包含单位换算、公式计算、附加费）
                 snapshot = result.get("item_snapshot", {})
+                if snapshot.get("cost_price") is not None:
+                    item_copy["cost_price"] = snapshot["cost_price"]
                 if snapshot.get("pricing_type"):
                     item_copy["pricing_type"] = snapshot["pricing_type"]
                 if result.get("area_sqm"):