The phenomenon of ricochet of projectile penetrating into concrete target is simulated by 3D FE-SPH adaptive coupling algorithm. Based on the time curve of velocity,acceleration,angular momentum and rotational moment of the ricochet process extracted from the numerical results,the process and cause of ricochet are analyzed. The results show that rotational moment caused by asymmetric resistance of concrete target exerting on projectile is the essential reason of ricochet. In view of the above analysis,some useful conclusions are drawn,such as the law of ricochet under different initial velocities,oblique angles and target thickness.