In this paper, the flow field and trajectory of supercavitating projectile are calculated. Based on Fluent software, the axisymmetric calculation model is established, and the numerical simulation method of projectile underwater high-speed trajectory is established. Firstly, the simulation calculation of cavitation shape in the velocity range of 90m/s~190m/s is carried out, which is compared with the classical formula to verify the effectiveness of the calculation method. Then, the numerical simulation of the projectile in the water with initial velocity of 80m/s-130m/s is carried out. The numerical results show that when the engine is not ignited and the initial velocity is 90m/s, the projectile shows a “head up” navigation trend, and no complete supercavitation is formed at this time. In the velocity range of 100m/s-130m/s, the overall motion of the projectile shows a “bow” trend, the projectile is completely wrapped by cavitation, and the projectile does not collide with the cavitation wall. After the engine generates thrust, the maximum range can reach 70m under the action of this thrust.