Hi , thanks for the reply, but I found I might not explain it clearly. First, I export a fbx file (one actor attach to another) from UE4 then I import it to maya( maya 2018). The result, it should be one parent and a child, shows different after maybe a day and it never looks correctly anymore. I mean I tried restart maya , restart UE4, change how I attach those actors(attach to component or actor), then I export a fbx file from UE4 4.19 to maya, and it looks perfectly fine. It seems to me maya has nothing to with this problem though.
So far I have no clue about it because I didn’t do anything other then attach actors and export it. I guess I will try deleting history to see what will happen.