Abstract: A new method for analyzing module reliability of Network Management System(NMS) in operational phase is proposed to resolve the problem existed in the domain of current NMS reliability evaluation. Firstly, some methods, e.g. periodic survival reports and module redundancy, which is used in NMS are assembled into three major run-time scenarios; Secondly, three scenario are modeled using Markov Regenerative Stochastic Petri Nets (MRSPN), and the effect which various scenario impose on module reliability is analyzed. Finally, some important reliability index, such as module availability, is concluded with applying the models. Numerical examples show that module reliability depend on both quality itself and run-time scenarios. Suitable run-time scenario can be applied in various modules according to the requirement of NMS.