This is one of the many serious things to consider when taking a job in China. Do your research before you do an interview with any Chinese company as once you do you are somewhat Locked In. After a contract expires you can ask for a letter of release and it should be forthcoming. Your contract should have had language requiring this release letter after contract termination along with a safety letter assuring no accidents or incidents and get the last 3 pages or your whole log books stamped before you completely separate. Once you leave town nothing will happen fast for you. If your previous employer refuses then use your new employer and if involved your recruitment agency. What most employers are after is the soft blue logbook which is your CAAC training records and Check Ride performance. My experience is it is best to not tell any Chinese employer where you are going. Just tell them you are taking a few months off from flying and considering your options but you desire all the required documents should you decide to fly again elsewhere. The new employer will have to get involved at some point to requ,est certain paperwork so heave them do the legwork if you cannot get what you need. You can always get a Chinese lawyer to write a nasty letter and threaten a breach of contract lawsuit. The Courts will not get involved but sometimes just the threat is enough. You can also have your attorney try and go through the Chinese Labor Bureau. Chinese employers treat an emploYee like a marriage and they don't like people moving around a lot as it looks bad upon their reputation. Again consider all these possibilities before taking a pilot job in China.