diff --git a/backend/app/http/v1/dto/order.go b/backend/app/http/v1/dto/order.go
index c4990e9..ec0bcbd 100644
--- a/backend/app/http/v1/dto/order.go
+++ b/backend/app/http/v1/dto/order.go
@@ -9,6 +9,8 @@ type OrderCreateForm struct {
 	Quantity int `json:"quantity"`
 	// UserCouponID 用户券ID（可选）。
 	UserCouponID int64 `json:"user_coupon_id"`
+	// IdempotencyKey 幂等键（同一业务请求需保持一致）。
+	IdempotencyKey *string `json:"idempotency_key"`
 }
 
 type OrderCreateResponse struct {
diff --git a/backend/app/services/order.go b/backend/app/services/order.go
index 8a38acf..63d5a4a 100644
--- a/backend/app/services/order.go
+++ b/backend/app/services/order.go
@@ -3,6 +3,7 @@ package services
 import (
 	"context"
 	"errors"
+	"strings"
 	"time"
 
 	"quyun/v2/app/errorx"
@@ -78,6 +79,22 @@ func (s *order) Create(
 	uid := userID
 	cid := form.ContentID
 
+	// 幂等控制：相同幂等键直接返回已创建的订单。
+	idempotencyKey := ""
+	if form.IdempotencyKey != nil {
+		idempotencyKey = strings.TrimSpace(*form.IdempotencyKey)
+	}
+	if idempotencyKey != "" {
+		tbl, q := models.OrderQuery.QueryContext(ctx)
+		existing, err := q.Where(tbl.UserID.Eq(uid), tbl.IdempotencyKey.Eq(idempotencyKey)).First()
+		if err == nil {
+			return &transaction_dto.OrderCreateResponse{OrderID: existing.ID}, nil
+		}
+		if !errors.Is(err, gorm.ErrRecordNotFound) {
+			return nil, errorx.ErrDatabaseError.WithCause(err)
+		}
+	}
+
 	// 1. Fetch Content & Price
 	content, err := models.ContentQuery.WithContext(ctx).Where(models.ContentQuery.ID.Eq(cid)).First()
 	if err != nil {
@@ -123,9 +140,12 @@ func (s *order) Create(
 		AmountDiscount: amountDiscount,
 		AmountPaid:     amountPaid,
 		CouponID:       couponID,
-		IdempotencyKey: uuid.NewString(),
+		IdempotencyKey: idempotencyKey,
 		Snapshot:       types.NewJSONType(fields.OrdersSnapshot{}),
 	}
+	if order.IdempotencyKey == "" {
+		order.IdempotencyKey = uuid.NewString()
+	}
 
 	err = models.Q.Transaction(func(tx *models.Query) error {
 		if err := tx.Order.WithContext(ctx).Create(order); err != nil {