diff --git a/YYModel/NSObject+YYModel.m b/YYModel/NSObject+YYModel.m
index 3d7c470..0c7960b 100644
--- a/YYModel/NSObject+YYModel.m
+++ b/YYModel/NSObject+YYModel.m
@@ -1160,7 +1160,8 @@ Returns a valid JSON object (NSArray/NSDictionary/NSString/NSNumber/NSNull),
  */
 static id ModelToJSONObjectRecursive(NSObject *model) {
     if (!model || model == (id)kCFNull) return model;
-    if ([model isKindOfClass:[NSString class]]) return model;
+    if ([model isKindOfClass:[NSString class]])
+        return [((NSString *)model) dataUsingEncoding:NSUTF8StringEncoding];
     if ([model isKindOfClass:[NSNumber class]]) return model;
     if ([model isKindOfClass:[NSDictionary class]]) {
         if ([NSJSONSerialization isValidJSONObject:model]) return model;