In order to study the impact of explosively formed projectile (EFP) on the impact of the cover explosives under different conditions, the numerical simulation model of EFP impact detonation shell explosive was established by Ls-Dyna simulation software. Using different head speeds in different stages of the EFP forming process, the impact initiation simulation of CompB explosives with different thickness covers was carried out, and the relationship between specific kinetic energy, head speed and thickness of the cover, the thickness of the cover, the change law of the detonation time and position were analyzed. The simulation results show that between 0.5 and 1 times the diameter of the charge, it can be concluded that the critical cover thickness is proportional to the head speed and the projected area of the EFP along the flight direction, and the EFP is penetrating more than 2.5 times the diameter of the charge. During the plate process, no shearing block is formed; The caliber 40 mm EFP designed in this paper is fully formed, its specific kinetic energy is 61.81 MJ/m2, and the maximum CompB explosive with a thickness of 10mm can be detonated; within a certain thickness of the cover plate, the impact both the detonation time and the impact detonation position increase with the increase of the thickness of the cover plate; when the EFP flies to the 0.5 times the diameter of the charge, the thickness of the critical cover plate capable of impacting and detonating is twice that of the EFP after molding. It has some reference value for EFP design of air defense antimissile warhead.