i have to visit to china for a fellowship of 6 weeks , what kind of visa i should apply and what is

Vivek, by "fellowship", do you mean a post which involves research work? If so, you shoud apply for an F type or Z type. Comparaviely speaking, it's easier to get the F type. To get it, you should submit your passport, a copy of the photo page of the pasport, a filled-out application form affixed with your full-face colore bare-headed photo against a white backgroud and an invitation letter from the relevant entity or individual in China.