A multilayer constrained alumina ceramic metal composite armor is designed in this paper. The effect of interlayer steel thickness of alumina ceramic metal armor on penetration process of tungsten alloy armor piercing projectile is studied by the penetration test and finite element simulation. The results show that in the case of the same layer of ceramics and equal surface density, the thicker the thickness of the steel plate away from the impact surface is, the better the support of the metal plate to the sandwich ceramics is. It is beneficial to maintain the initial volume of ceramics and the better ballistic performance of armor. The ballistic performance of the armor structure in this paper is 26.38 % higher than that of the Q235 steel plate with equal density.