The validity period of the residence registration is normally the same as the validity period of the visa (the validity period of residence registration for foreigners whose country has mutual visa exemption arrangement with china is usually one year).
If you cannot leave China before the validity of your residence registration expires, you must request the entity you work for or that hosts you to state to the Chinese visa authorities the reason and length of extension in a note (official letter) attached with valid passport at least three days before the expiry of your residence registration for extension of your residence registration.
(english.gov.cn)
