A calculation model based on the cavity expansion theory is developed to predict the overloading on the truncated-conical projectile penetrating into finite thickness metallic plates at low speed. The influences of the velocity of the projectile, the projectile taper and the strength of the target material on the overloading are analyzed. The results show that the velocity of the projectile has a noticeable effect on the magnitude of overloading but a much less important effect on the period of the overloading; both the projectile taper and the strength of the target material have a significant effect on the magnitude and the period of the overloading, the magnitude and the period decrease as the taper and the velocity decrease. The predicted results are in good agreement with experimental results, which has validated the model.