In order to explore the process and mechanism of high pressure water jet cutting and breaking natural gas hydrate reservoir of the South China Sea, LS—DYNA3D code had been used to simulate the process of water jet breakup of hydrates in submerged state. The effect of different jet velocities on the crushing effect of hydrate bearing sediments under high pressure water jet was studied. The erosion depth increases linearly with the jet velocity. The erosion volume of hydrates sediment is the result of axial erosion and radial erosion. The greater the jet velocity is, the axial and radial erosion of hydrate deposits are enhanced, and the increasing rate of the erosion volume of the hydrate deposits is increased.