Online academic social platform provides researchers with a new way of academic social interaction. This study attempts to examine the user behaviors of online academic social platform from the perspective of user usage. Users of ResearchGate in Nanjing University as the research object and their behavioral characteristics are examined with the correlation analysis and social network analysis about their activity, behaviors, cooperation network and so on. The research discovers that the status of users' usage on the platform is influenced by the background of their academic subject to a large extent, for instance, the users majored in science and technology are far more active than others; There exists a relationship among uploading, reading and citing behaviors; It is easier to generate a stable cooperative group when users in school retain working with the external users.