Facebook is currently the most popular social networking service in the world. With such tremendous influence on community networks, Facebook has been attracting considerable attention both from the media and academia. A review of the literature indicates that most researchers are concerned primarily with the influence of personal traits on online interactive behavior. This study began from the premise that self-efficacy, the confidence of individuals to function in an online-community, is a key element influencing participation in on-line social networks. This study attempted to establish a model of the social traits of Facebook users, and our results indicate that social self-efficacy has a positive influence on social trust; social trust has a positive influence on social capital, and social trust mediates the relationship between social self-efficacy and social capital.