diff --git a/deps/oblib/src/common/object/ob_object.cpp b/deps/oblib/src/common/object/ob_object.cpp
index 4794b04d3f5e0eedb6f09861435dc6ec3553073c..18e0a9284609e3bb3e143ca42255f60d19fd9808 100644
--- a/deps/oblib/src/common/object/ob_object.cpp
+++ b/deps/oblib/src/common/object/ob_object.cpp
@@ -276,6 +276,7 @@ DEF_TO_STRING(ObLobLocator)
 const char* ObObj::MIN_OBJECT_VALUE_STR = "__OB__MIN__";
 const char* ObObj::MAX_OBJECT_VALUE_STR = "__OB__MAX__";
 const char* ObObj::NOP_VALUE_STR = "__OB__NOP__";
+const char OB_JSON_NULL[2] = {'\0', '\0'}; // binary json null 
 
 OB_SERIALIZE_MEMBER(ObDataType, meta_, accuracy_, is_zero_fill_);
 OB_SERIALIZE_MEMBER(ObEnumSetInnerValue, numberic_value_, string_value_);
@@ -458,12 +459,14 @@ int ObObj::build_not_strict_default_value()
     case ObTinyTextType:
     case ObTextType:
     case ObMediumTextType:
-    case ObLongTextType: 
-    case ObJsonType: {
+    case ObLongTextType: {
       ObString null_str;
       set_string(data_type, null_str);
       meta_.set_lob_inrow();
     } break;
+    case ObJsonType: {
+      set_json_value(data_type, OB_JSON_NULL, 2);
+    } break;
     case ObBitType:
       set_bit(0);
       break;
diff --git a/deps/oblib/src/lib/mysqlclient/ob_mysql_result.h b/deps/oblib/src/lib/mysqlclient/ob_mysql_result.h
index d3afdce7fe072eca7bea2a1c3f717e823204b9af..91c3b1369ed4a2a9175f3c85bb58b559ae610ab6 100644
--- a/deps/oblib/src/lib/mysqlclient/ob_mysql_result.h
+++ b/deps/oblib/src/lib/mysqlclient/ob_mysql_result.h
@@ -686,7 +686,34 @@
           }                                                                                               \
           ret = (class_obj).set_##column_name(dest_obj);                                                  \
         }                                                                                                 \
-      } else {                                                                                            \
+      } else if (ob_is_json(data_type) && share::is_mysql_mode())                                         \
+      { /* MySQL json does not support default value except null, */                                      \
+        /* need this defensive to compatible a bug in old version */                                      \
+        ObObj def_obj;                                                                                    \
+        ObObj default_value;                                                                              \
+        default_value.set_type(data_type);                                                                \
+        ObArenaAllocator allocator(ObModIds::OB_SCHEMA);                                                  \
+        ObObj dest_obj;                                                                                   \
+        ObCastCtx cast_ctx(&allocator, NULL, CM_NONE, column.get_collation_type());                       \
+        if (OB_FAIL(default_value.build_not_strict_default_value())) {                                    \
+          SQL_LOG(WARN, "failed to build not strict default json value", K(ret));                         \
+        } else {                                                                                          \
+          def_obj.set_json_value(data_type,                                                               \
+                                 default_value.get_string().ptr(),                                        \
+                                 default_value.get_string().length());                                    \
+          if (OB_FAIL(ObObjCaster::to_type(data_type, cast_ctx, def_obj, dest_obj)))                      \
+          {                                                                                               \
+            SQL_LOG(WARN, "cast obj failed, ", "src type", def_obj.get_type(), "dest type", data_type);   \
+          }                                                                                               \
+          else                                                                                            \
+          {                                                                                               \
+            dest_obj.set_lob_inrow();                                                                     \
+            dest_obj.meta_.set_collation_level(CS_LEVEL_IMPLICIT);                                        \
+            ret = (class_obj).set_##column_name(dest_obj);                                                \
+          }                                                                                               \
+        }                                                                                                 \
+      }                                                                                                   \
+       else {                                                                                             \
         ObObj def_obj;                                                                                    \
         def_obj.set_varchar(str_value);                                                                   \
         ObArenaAllocator allocator(ObModIds::OB_SCHEMA);                                                  \
@@ -699,14 +726,7 @@
         } else if (OB_FAIL(ObObjCaster::to_type(data_type, cast_ctx, def_obj, dest_obj))) {               \
           SQL_LOG(WARN, "cast obj failed, ", "src type", def_obj.get_type(), "dest type", data_type);     \
         } else {                                                                                          \
-          if (ob_is_json(data_type)) {                                                                    \
-            dest_obj.set_lob_inrow();                                                                     \
-            dest_obj.meta_.set_collation_level(CS_LEVEL_IMPLICIT);                                        \
-          }                                                                                               \
-          else                                                                                            \
-          {                                                                                               \
-            dest_obj.set_scale(column.get_data_scale());                                                  \
-          }                                                                                               \
+          dest_obj.set_scale(column.get_data_scale());                                                    \
           ret = (class_obj).set_##column_name(dest_obj);                                                  \
         }                                                                                                 \
       }                                                                                                   \