i find a job in china now what i can ask that employer for visa or for what?

You can ask the employee to provide you with the following two documents:
(1)Original invitation or confirmation letter from an authorized government organization like the local foreign affairs office in China;
(2) and Registration Certificate of Foreign Enterprises Permanent Office in China/Alien Employment License of the P. R. China/Working Permit by the State Administration of Foreign Experts Affairs, China