When a work visa is nearly expired a foreigner is expected to leave the country but it is common to extend the visa for tourism or business. You will have to go to Immigration and ask for this. Granting an extension is their decision not yours. Just tell them you want to tour China or close your bank accounts, pack your bags, etc. There is usually a modest fee for extending a visa. Every country is different. Do not go late. The fines are very high!