The emergence of social network application and rapid development, makes the human use of the Internet has a great way to change. An in-depth understanding of the online social networks is necessary to insight into questions of human social behavior, study the structure of online social network, to design future online social network, and to understand the impact of online social networks on the Internet. In this paper, we present a brief review of the related work on social networks. Social network research mainly includes three aspects: the structure characteristics of the social network, user group and its behavior, and information dissemination and influence analysis in social network.