Is it possible to get ordinary visa to China within 7 days Or which visa we can take?

yes, it is possible, and you can use urgent or exreme urgent service for visa processing if you need. You need to apply for a China tourist visa and then a Tibet Travel permit. For documents required, they are passport, application form, photo, Invitation letter (if visit for the first time). If you cannot provide invitation letter, you can provide a visa recommendation letter from your company. Besides, bank statements, round-trip air tickets booking are also required. However, I have heard that it is very hard to get Tibet Travel Permit now, so you'd better contact a China travel agency to get the latest information.