A mesomechanic reaction model of heterogeneous explosives under shock wave was established. In this model,“hot spot” was formed as a result of the elastic-viscoplastic collapse induced by shock,while the growth stage started from an inner combustion and was followed by an outer surface grain combustion. Then the model was implemented in one-dimensional reactive hydrodynamic program SSS and a genetic algorithm was used to decide the target parameters in the model of reaction rate in PBX-9404.