Determining maintenance demand ahead of mission is crucial to practical weapon maintenance, especially to regional warship weapon maintenance. While determining the regional warship weapon maintenance demand, attention is paid only to reliability, but the nature of mission or the consequence of damage is ignored. For this reason, a method for determining regional maintenance demand based on simulation is put forward in this paper. Regional weapon maintenance system is first analyzed to build a mission-oriented maintenance demand model based on the concept of mission-induced failure. Subsequently, the Anylogic platform is employed because of its advantages including agent modeling simulation and visualized process display. Four types of agent are designed for the regional maintenance system. The process of determining maintenance demand based on simulation is established on this basis. At last, an example is taken to calculate and verify the universality and effectiveness of the simulation model.