To study the vibration characteristics of supercavitating projectiles under tail-slapping conditions,the fundamental frequency and the first principal mode shape of the transverse vibration of projectiles were presented,based on the dynamics of coupling system for rigid and elastic motions.By simulations,the influences of rotational speed,slenderness ratio and material characteristics on frequency and the mode shape of vibration were investigated.The results show that the frequency and the mode shape vary with the rotational speed,and the increase of the slenderness ratio and the material characteristic parameter could accelerate these variations.For the small slenderness ratio or the rotational speed is less than 50 rad/s,the influence of coupled motions can be disregarded and the natural frequency can be used as the frequency of vibration,and the natural mode shape also can be used when the rotational speed is less than 100 rad/s.