Team formation problem has received extensive study in operational research (OR). Recently, along with the popularity of various social sites and the rapid development of Internet communication, team formation in social networks has attracted great study enthusiasm of scholars once again. Team formation problem in social networks differs much from the traditional team formation which takes no account of the social relations and effective communication in a team. Thus it cannot be solved simply by means of set-cover, task assignment or maximum matching any more. Based on sufficient research and analysis, this work surveys the state of the art of the social-based team formation problem. The variants of this problem and their optimization methods are reviews as well. In the meantime, the data-sets and evaluation criteria of experiments in this study are introduced. Finally, the prospect of future work is presented.