Abstract: Computational fluid dynamics was used in high velocity air fuel spraying flow field simulation. The right place to transport powder was chosen according to the simulation results. The influence of injection angle (θ), WC 10Co4Cr particles incident flow (M), particle diameter (D), and injection velocity (v) were studied. There are two places to inject powder, distance the nozzle length of 5 times the nozzle diameter and the length of 20 times. When injection angle ranges from 30° to 50°, WC 10Co4Cr particles incident flow is 1 g/s, particle diameter is about 50 μm, the flight trajectory is the best. When the velocity is about 30 m/s, trajectories of the particles is the best. However, there will be a serious phenomenon of particle collisions when the velocity is more than 35 m/s.