Residence Permit for Foreigner in the Peoples Republic of China

Question please-my employer recently moved back to the USA from working in China. He has a Residence Permit for Foreigner in the Peoples Republic of China that is still valid until December 31 2012. Can he return to China using this document, or will he need to get a Visa? I am planning a business trip for him in the near future and i dont know if I need to get him a visa or if this document will still suffice.