Cloud manufacturing (CMfg) is a novel business paradigm with resource service (RS) sharing being one of the most important purposes. From the perspective of enterprise business interactions, how to achieve full RS sharing is an important research issue in CMfg as it plays a critical role in enhancing the performance and efficiency of a CMfg system. However, the research on CMfg RS sharing is challenged by the complexity of a CMfg system, mainly coming from the vast number of involved enterprises and their complex business interactions. In this paper, we propose a modeling framework for CMfg RS sharing by regarding a CMfg system as a complex system and elaborating the problem from the perspective of complex systems modeling and simulation. We summarize systematically the factors that need to be considered for building a system of CMfg RS sharing, which is followed by the modeling procedure.