Ms.Ary, besides the Admission Letter from a unversity in China, you also should have A visa application form for international students (JW201 or JW202) issued by the Ministry of Education of China. Then you can apply for student visa (X visa), generally speaking, the student visa is single entry, valid for 3 month and no duration of stay. Applicants should apply for a residence permit from a local county level Public Security Bureau within 30 days after entering China. The residence permit looks like a visa pasted on your passport.