Nowadays, online games have become a highly profitable e-commerce application. Therefore, researchers increasingly believe that understanding online game player behavior is critical to the success of online game practitioners.The factors influencing the flow of online games are of major concern to academic researchers and online games practitioners. Drawing on the theory of flow, this study empirically explores how the interactivity and intrinsic beliefs impact flow experience, and how flow experience is related to replay intention. Then, confirmatory factor analysis is applied to test and the proposed research model is evaluated with partial least squares (SmartPLS 2.0). The results show that flow experience is a significant predictor ofreplay intention. Four antecedents to flow (telepresence, focused attention, skills and challenges) have positive influence on flow experience. Interactivity (social interactivity and human-machine interactivity) and intrinsic beliefs (perceived attractiveness, personal involvement) influence the antecedents of flow experience. Moreover, social interactivity has a stronger impact on the antecedents of flow experience than human-machine interactivity. This study finds that social interactivity is most crucial to online game success.