diff --git a/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPortalOrderServiceImpl.java b/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPortalOrderServiceImpl.java
index 0c35e4e7d1..1df5089eed 100644
--- a/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPortalOrderServiceImpl.java
+++ b/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPortalOrderServiceImpl.java
@@ -673,9 +673,21 @@ private void handleCouponAmount(List<OmsOrderItem> orderItemList, SmsCouponHisto
      */
     private void calcPerCouponAmount(List<OmsOrderItem> orderItemList, SmsCoupon coupon) {
         BigDecimal totalAmount = calcTotalAmount(orderItemList);
-        for (OmsOrderItem orderItem : orderItemList) {
-            //(商品价格/可用商品总价)*优惠券面额
-            BigDecimal couponAmount = orderItem.getProductPrice().divide(totalAmount, 3, RoundingMode.HALF_EVEN).multiply(coupon.getAmount());
+        BigDecimal couponAmountTotal = coupon.getAmount();
+        BigDecimal remainingAmount = couponAmountTotal;
+        int size = orderItemList.size();
+        for (int i = 0; i < size; i++) {
+            OmsOrderItem orderItem = orderItemList.get(i);
+            BigDecimal couponAmount;
+            if (i < size - 1) {
+                //(商品价格/可用商品总价)*优惠券面额
+                couponAmount = orderItem.getProductPrice().divide(totalAmount, 3, RoundingMode.HALF_EVEN).multiply(couponAmountTotal);
+                remainingAmount = remainingAmount.subtract(couponAmount);
+            } else {
+                // last item gets the remainder to ensure total equals coupon amount
+                couponAmount = remainingAmount;
+            }
+            couponAmount = couponAmount.setScale(2, RoundingMode.HALF_UP);
             orderItem.setCouponAmount(couponAmount);
         }
     }
diff --git a/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPromotionServiceImpl.java b/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPromotionServiceImpl.java
index 73a3351cb0..bbec4267c2 100644
--- a/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPromotionServiceImpl.java
+++ b/mall-portal/src/main/java/com/macro/mall/portal/service/impl/OmsPromotionServiceImpl.java
@@ -88,10 +88,10 @@ public List<CartPromotionItem> calcCartPromotion(List<OmsCartItem> cartItemList)
                         BeanUtils.copyProperties(item,cartPromotionItem);
                         String message = getFullReductionPromotionMessage(fullReduction);
                         cartPromotionItem.setPromotionMessage(message);
-                        //(商品原价/总价)*满减金额
+                        //(商品原价/总价)*满减金额，使用 multiply-divide 顺序避免 divide 精度损失
                         PmsSkuStock skuStock= getOriginalPrice(promotionProduct, item.getProductSkuId());
                         BigDecimal originalPrice = skuStock.getPrice();
-                        BigDecimal reduceAmount = originalPrice.divide(totalAmount,RoundingMode.HALF_EVEN).multiply(fullReduction.getReducePrice());
+                        BigDecimal reduceAmount = originalPrice.multiply(fullReduction.getReducePrice()).divide(totalAmount, 2, RoundingMode.HALF_EVEN);
                         cartPromotionItem.setReduceAmount(reduceAmount);
                         cartPromotionItem.setRealStock(skuStock.getStock()-skuStock.getLockStock());
                         cartPromotionItem.setIntegration(promotionProduct.getGiftPoint());