diff --git a/inventory-backend/app/services/trans_service.py b/inventory-backend/app/services/trans_service.py
index 6b5afee..1f10c57 100644
--- a/inventory-backend/app/services/trans_service.py
+++ b/inventory-backend/app/services/trans_service.py
@@ -381,10 +381,14 @@ class TransService:
                 if ModelClass:
                     stock = ModelClass.query.with_for_update().get(record.stock_id)
                     if stock:
-                        stock.stock_quantity = float(stock.stock_quantity or 0) - pending_qty
-                        # 防止负库存
-                        if stock.stock_quantity < 0:
-                            stock.stock_quantity = 0
+                        stock_qty = float(stock.stock_quantity or 0)
+                        # 不足则报错整单回滚：直接夹到 0 会让 available_quantity > stock_quantity，
+                        # 凭空多出可用库存
+                        if pending_qty > stock_qty:
+                            raise ValueError(
+                                f"SKU {record.sku} 实物库存不足（剩 {stock_qty}），无法报废 {pending_qty}"
+                            )
+                        stock.stock_quantity = stock_qty - pending_qty
 
                 # 3. 创建报废记录
                 scrap_record = TransScrap(