The aim of this study is to execute the fluid dynamics simulation of high speed jet under distinct input velocities (i.e., 114.1, 142.4, 165.6, 186.2 and 286.9 m/s). In particular, this study focuses on the impact velocity and velocity of two-phase flow (gas-liquid). Firstly, the three-dimensional geometric model of high speed jet is established on the basis of the actual operational conditions. Next, the unstructured grids of high speed jet are generated by means of ANSYS Fluent. Finally, the fluid dynamics simulation of high speed jet is implemented by using Fluent. The simulation results show that when the input velocity of the liquid increases, the impact velocity declines sharply, while according to the Bonuli law of conservation of energy, the impact effect on the device shows exponential growth with increasing input velocity. In addition, the relationship between the impact velocity and the input velocity and the relationship between the impact effect on the device and the input velocity are achieved, which could provide certain theoretical guidance for predicting the working pressure and velocity of high speed jet based on real input velocity.