Do I need to apply for a visa to visit China Changchun for about 18days?

1.Yes, you need a China L visa to visit China;
2.You shall apply at the China Visa Application Service Centre(CVASC) located at 9th Floor, Royal Brothers, 22 Malacca Street, CVASC will collect visa fees on behalf of the Embassy. I suggest you'd better apply visa one month in advance of your intended date of entry into China;
3.Before the application,you shall prepare all the required documents including original passport with at least two blank visa pages,and for single entry visa, your passport should be valid at least 6 months;one completed Visa Application Form with a recently-taken passport photo stuck on it;and round-trip airline tickets and hotel reservation;
4.Make an appointment via the official web of the center.Then you can submit your visa application to the Centre in person or entrust someone or a travel agency to submit on your behalf. Application by post is currently not accepted;
5Regularly you can get the visa on the fourth working day. The Centre offers express service and rush service. For express service, visa will be ready for collection on the third working day. For rush service, visa will be ready for collection on the second working day.