To obtain the water-entry cavitation evolution and motion characteristics of supercavitation projectiles in different attack angle, the water-entry process of constant water-entry speed and different attack angle in hydrostatic and wave environment is simulated by using RANS equation, k-ε turbulence model, Schnerr-Sauer cavitation model and overset mesh. The result shows that the projectile will have an obvious tail-slap phenomenon in the process of water-entry when the attack angle is larger than 2°. When tail-slap phenomenon occurs, the tail wing cuts through the cavity wall, which cause the expansion of the cavity in this area and adversely affect the trajectory stability. Furthermore, both the drag and lift coefficients will rise, and the higher the angle of attack, the greater the rise. In the wave environment, the tail-slap phenomenon will still occur in the process of the projectile entering the water, but compared with the static water environment, there is a certain difference in the time of the tail-slap. When the attack angle is positive, the time of the tail-slap is advanced, otherwise it will be delayed.