How to make use of Inter organizational Information System (IOS) to assist operation, management and decision making, so as to bring competitive advantage for enterprises has become an unavoidable problem for modern enterprises. Based on the concepts and theories of enterprise dominant power, social capital and IOS assimilation, this paper constructs a moderating model of enterprise dominant power in the impact of social capital on IOS assimilation, aiming to clarify the different impact paths and moderating mechanisms of social capital on IOS assimilation in enterprises with different dominant power.Moreover, this paper makes an empirical test on moderating effects based on three analyses methods: introducing interactive items, calculating variance ratio between moderating effect model and main effect model, judging explanation increment. The results show that enterprise dominant power plays an important role in moderating the impact of three different dimensions of social capital (structural capital, relationship capital and cognitive capital) on IOS assimilation. It is of great theoretical and practical significance for enterprises with different dominant powers to promote the assimilation of IOS and improve the potential value of information system.