diff --git a/desc/inference/inference.api b/desc/inference/inference.api
index 87b9f7fd..13ccda23 100644
--- a/desc/inference/inference.api
+++ b/desc/inference/inference.api
@@ -35,8 +35,8 @@ type (
      /******************image inference*************************/
      /******************instance center*************************/
      InstanceCenterReq{
-          InstanceType    int32   `json:"instance_type"`
-          InstanceClass   string   `json:"instance_class"`
+          InstanceType    int32    `form:"instance_type"`
+          InstanceClass   string   `form:"instance_class,optional"`
      }
      InstanceCenterResp {
           InstanceCenterList []InstanceCenterList `json:"instanceCenterList" copier:"InstanceCenterList"`
diff --git a/internal/types/types.go b/internal/types/types.go
index 271fcb36..9bef1f4a 100644
--- a/internal/types/types.go
+++ b/internal/types/types.go
@@ -3666,8 +3666,8 @@ type InstanceCenterList struct {
 }
 
 type InstanceCenterReq struct {
-	InstanceType  int32  `json:"instance_type"`
-	InstanceClass string `json:"instance_class"`
+	InstanceType  int32  `form:"instance_type"`
+	InstanceClass string `form:"instance_class,optional"`
 }
 
 type InstanceCenterResp struct {