The flat-nose projectile low-velocity penetration in clay soil was simulated with various ranges of caliber and impact velocities by using ANASYS-AUTODYN software. The penetration depth and crater shape were in agreement with the results of laboratory experiment. The penetration depths of various initial conditions were discussed. The results demonstrated that the penetration depth keeps a linear relationship with impact velocity and the penetration depth appears linearly increase with the impact velocity upwards. The increment of penetration depth caused by doubling projectile caliber approximatively keeps constant.