The behavior studies on projectile penetrating 603-typed armor are carried out both in simulation and experiment. Initial discoveries involving the affect of impact velocity and impact angle on penetration acceleration are obtained. Simulations of AUTODYN-3D hydrocode show that impact velocity and impact angle affect the penetration acceleration significantly. Penetration acceleration increases as impact velocity increases; however it appears a contrary trend as impact angle increases. The witness experiments of 56mm diameter projectile with different impact velocities penetrating 603-typed armor show a quite good agreement with the simulations, and penetration acceleration increases as impact velocity increases, and the maximum acceleration appears in the time range of 0.05—0.2ms.