The anti-penetration performance of metal target plate has always been a focus of research. In order to clarify the influence of structural parameters on the vertical penetration resistance of steel/aluminum composite structures, numerical calculation models of steel and aluminum composite structures were established and verified by ballistic impact tests. Based on the numerical model, the influences of the combination form of steel-aluminum, al-steel and target spacing on the penetration resistance of the composite target with the same thickness were analyzed. The simulation results show that under the same thickness, the combination form of steel plate in front was better than the target plate with aluminum plate in front, but the different combination form of laminar spacing has little influence on its anti-penetration performance. In addition, the influence of the thickness ratio of steel to aluminum on the penetration resistance of the composite target plate at different initial velocities was compared. The penetration resistance of the composite target plate decreases first and then increases with the increase of the thickness ratio, and finally reaches a stable value. There is a low point with the worst penetration resistance during the change process, which should be avoided as much as possible in structural design. Finally, the trajectory limit formula of musketeer projectile penetrating steel-aluminum composite structure was obtained by fitting the simulation data according to THE R-I formula. The research results can provide reference for the design of anti-penetration performance of composite target plate and the protection of personnel and materials.