Are you part of the school's faculty?  If that is the case, then the retirement plan is probably a 403(b). 

You can get your contribution back, but the school's matching part depends on its policy, usually the longest vesting period would be 5 years.

If you leave, then you have a couple of options to take the money out.  And depending on which one you choose, it may or may not make sense for you to join this plan.

The best option is to rollover the money into an IRA, and not withdraw it.  If you plan to use this money when you go back to China, then it may not be a good idea to join the plan.