The numerical simulation on spray characteristic of pressure swirl nozzle was carried out,and the main factors effecting the atomizing performance of the nozzle were studied.The distributions of velocity and diameter of droplets were obtained at different special sections.Simulation results were compared with the experimental results.The simulation results indicate that the droplet size is proportional to pressure and nozzle diameter,and inversely proportional to viscosity and surface tension of liquid.Along the spray axis,droplet velocity decreases acutely,and keeps steady at the downstream of 200 mm.Along the radial direction,the axial velocity of droplet in the center is lower than that on the edge,where the droplet size is maximum.Due to droplet collision and breakup,the droplet size decreases first,and then slowly increases.The simulation results are in good agreement with experimental results.