Aiming at the problem of penetration performance of armor piercing projectile, a simple quilt cap design method is given. This paper describes the basic factors of low-speed armor-piercing ricochet, expounds the design principle of simple quilt cap structure, and introduces the influence on inclined armor-piercing performance. The numerical analysis and flight test results show that the method can prevent the projectile from ricocheting and protect the main penetration structure of the projectile from breaking when hitting the target, and improve the penetration ability of the projectile by about 10%.