Despite considerable efforts have been devoted to study consumer loyalty, there is a lack of knowledge concerning how online service loyalty is or can be established in a competitive e-service market, in which several major service providers coexist to compete for customers. In this study, we attempt to explore the industry environment of Chinese social networking service (SNS), and examine the association between consumer satisfaction and switching costs in building service loyalty. From a resource-based view, unique service resources of SNS (critical mass and supplemental entertainment) are examined regarding their potentials in enhancing consumer satisfaction, habit and switching costs. The results show that habit and the interaction effect of satisfaction and switching cost are the key determinants of SNS loyalty. Critical mass and supplemental entertainment directly or indirectly affect habit and switching costs. This study attempts to bring the thought of competitive environment into e-service loyalty research while new insights for e-service loyalty building in different market environments are discussed.