In order to study the damage effect of 7.62 mm armor-piercing bullet on ceramic/aramid/ultra-high molecular weight polyethylene (PE-UHMW) composite armor, the penetration of the bullet into composite armor was simulated. By analyzing the formation, crack propagation and splashing process of the ceramic cone in the damage effect, the damage mode of the projectile body to the aramid fiber and PE-UHMW was analyzed, and the influence of different projectile velocities on the damage effectiveness of the composite armor was studied. The results show that the FEM-SPH coupling algorithm can well simulate the process of projectile penetrating ceramic/aramid/PE-UHMW composite armor. When the projectile velocity is less than the ballistic limit, the energy absorption and the maximum deformation of the back plate of the composite armor increase with the increase of the projectile velocity. When the projectile velocity is greater than the ballistic limit, the rate of energy absorption of the composite armor begins to decrease.