To address the problems of current approaches in software process reuse, in particular the low efficiency in reuse for the operational rules and for the lack of a precise definition of process components, a formalized approach for componentized software process modeling (CSPM) is presented in this paper. CSPM provides a mechanism to support the formal definition of reusable software process components and presents a series of rules to turn process components into a process model. By using CSPM, the reusage of process components can be conducted in a rigorous manner, and the potential errors caused by ambiguity in traditional non-formal modeling methods can be effectively avoided. CSPM can also turn the verification of a combined process model, against certain properties, into a series of sub-problems into its own corresponding components, making an original infeasible problem, under certain circumstances, into feasible ones by exponentially reducing the state space needed to be explored.