diff --git a/native_engine/impl/ark/native_value/ark_native_string.cpp b/native_engine/impl/ark/native_value/ark_native_string.cpp
index e519709..c20fb3e 100644
--- a/native_engine/impl/ark/native_value/ark_native_string.cpp
+++ b/native_engine/impl/ark/native_value/ark_native_string.cpp
@@ -45,9 +45,9 @@ void ArkNativeString::GetCString(char* buffer, size_t size, size_t* length)
     LocalScope scope(vm);
     Global<StringRef> val = value_;
     if (buffer == nullptr) {
-        *length = val->Length();
+        *length = val->Utf8Length() - 1;
     } else if (size != 0) {
-        int copied = val->WriteUtf8(buffer, size) - 1;
+        int copied = val->WriteUtf8(buffer, val->Utf8Length());
         buffer[copied] = '\0';
         *length = copied;
     } else {
@@ -86,7 +86,7 @@ size_t ArkNativeString::EncodeWriteUtf8(char* buffer, size_t bufferSize, int32_t
             break;
         }
 
-        str->WriteUtf8((buffer + pos), writableSize);
+        str->WriteUtf8((buffer + pos), str->Utf8Length());
         writableSize -= len;
         pos += len;
     }