Abstract: To investigate the influence of cavitator shapes on the motion characteristics of a supercavitating projectile during its tail-slap process, a three-dimensional free tail-slap motion simulation model was established based on the finite volume method and Mixture multiphase flow model, combined with the dynamic mesh technology. Under the conditions of different aspect ratios, the motion characteristics of projectiles with a flat head, a notched head and a conical head were compared during the tail-slap processes and the hydrodynamic factors were analyzed. When the aspect ratios are small, the motion of the projectile with a flat head kept stable, while the projectiles with a notched head and a conical head were prone to instability. The main reason was that the critical instability angle of attack decreased successively due to the differences of cavity size generated by the cavitators. When the aspect ratios are large, all three types of projectiles kept the tail-slap stable with the disappearance of the critical instability angle of attack. The projectile with a conical head kept stable in the "unilateral tail-slap" mode at high speeds, and in the "bilateral tail-slap" mode at a lower speed. The projectiles with a flat head and notched head were always stable in the "bilateral tail-slap" mode. For the projectiles with a flat head and notched head, vertical displacement in the same direction as the initial disturbance was produced due to the lifting force of warhead, while the direction was opposite for the projectile with a conical head due to the "unilateral tail-slap" mode.