pyFileUpload is the property which contains the filename. Use the option "Watch" in tracer to identify the point where the value of this property is getting changed.
Also, it might be possible that your application server doesn't support chinese characters due to which the filename is getting changed when the file gets uploaded to the server. Check with your admin team if the server has the required encoding to support the characters being used. UTF-8 encoding is capable of handling all the characters.