Abstract: Kinematic and dynamic analysis on underwater high-speed supercavitating projectiles were carried out and a mathematical model was proposed to establish coupling nonlinear differential equations. The equations were resolved to obtain the kinematical characteristics of the projectiles. The numerical simulation results show that the horizontal velocity of the flying projectile decreases rapidly because of the drag forces acting on the tip and the tail of the projectile. The angular velocity of the flying projectile decreases gradually in the fluctuating form, namely, a tail-slap phenomenon. Meanwhile, the vibration extent reduces gradually resulted from the lessening of the cavity dimension. The smaller the projectiles moment of inertia is, the less the changing range of the angular velocity and the tail-slap times are. The greater the launching depth or velocity is, the faster the tail slap attenuation is. The higher initial angular velocity can cause the angular velocity of the projectile to attenuate more rapidly.