Computational fluid dynamics(CFD) method was used to simulate the multiphase flow field of high pressure waterjet.The dynamic characteristics of abrasive waterjet,such as the water and particle velocities for the flow downstream under steady state,turbulent,two-phase and three-phase flow conditions were studied.The jet-characteristics comparisons between high-pressure waterjet and abrasive waterjet were performed under submersion and non-submersion.The visualizing pictures and simulation results were analyzed and researched,and its numerical results show that abrasive waterjet under non-submersion is the major process for high pressure water cutting tools.