how do we get the group visa for attend the Cantan Fare.what are the document that we have to provid

You need business visas to attend Cantoon Fair. The group visa is usually for tour groups. FYI: http://lk.china-embassy.org/eng/lsyw/visaaffairs/t174140.htm You may confirm whether business group visa is available for you or not. The requirements for a seperate business visa are: passport, a recent passport photos, visa application form V2011A, invitation letter from Cantoon Fair, "Invitation Letter of Duly Authorized Unit" or "Confirmation Letter of Invitation" and probably hotel reservation, return ticket and financial proof.