Aiming at the issue of low firing rate when hitting reverse slope targets at small impact angle, the modeling and analysis of the multi-level dynamic system were studied. Under multiple parameter conditions with impact angles below 10°, the dynamic simulation was done to ensure result accuracy. The Level-I external ballistic system determines the state of the impact point. Through Level-II projectile-target encounter simulation, impact overload responses are obtained and used as excitation for the Level-III firing mechanism system. The results reveal firing response patterns of fuze, guiding the optimized design of inertial firing mechanism. Optimized results demonstrate successful firing, confirming the reference value of the research.