Abstract: Based on the mechanisms of ceramic composite target against APP (amour-piercing projectile), an approximation to the deformation and cracking of ceramic composite target’s back plate was proposed, in which the impact action of APP onto the back plate through ceramic cone was equated with truncated-cone-shape localized impulsive load. According to the proposed approximation, the deformation of back plate and ballistic limits of some ballistic experiments of ceramic/mild steel composite target against 7.62mm APP were simulated with the finite element method code, ANSYS/LS-DYNA. The results from the numerical simulation are in good agreement with those from the ballistic experiments. The influnce of boundary conditions on the cracking of back plate was discussed, and the numerical and experimental results show that deformation at the back plate boundary can improve the rupture impulse of back plate and the ballistic limit of target.