Simulation of the velocity field of gas-solid-liquid three-phase flow inside and outside the abrasive water jet nozzle was studied by the computational fluid dynamics software (CFD). The complicated velocity field of the flow in the abrasive water jet (AWJ) nozzle and the abrasive track in the nozzle were obtained. In the course of the simulation, the inter-phase drag exchange coefficient model uses Gidaspow model (gas-solid), Wen-yu model (water-solid), Schiller-Naumann model (water-gas) respectively. The simulation results indicate that the swirl is produced in the nozzle and the abrasives are accelerated and moved around the swirl, and they are all distributed along the inner surface of the nozzle, the gas is mostly distributed in the center of swirl. The dispersion of the flow happens when it flows out of the nozzle, it can be divided into three zones, that is core zone, middle zone and border zone. At the core zone the velocity changes little while the velocity changes greatly at the middle zone, the velocity fluctuates greatly at the border zone.