Abstract: Numerical simulation on flow characteristics in a swirl nozzle has been carried out at pulsating pressures, while how following factors vary with the pressure pulsating frequency analyzed, such as the instantaneous flow, average flow, atomization angle and the phase difference between the pulsating pressure and the instantaneous flow, etc. Results show that the instantaneous flow and atomization angle change periodically at the same frequency as the pulsating pressure, and the phase difference between them is π; the average flow at nozzle outlet changes in an oscillatory way with the rise of pressure pulsating frequency, of which the variation law is relatively complicated.