Abstract: Theoretical studies and numerical simulation on dynamic characteristics of an open-end swirl injector were performed.The response of the injector flow to external excitations was investigated by superimposing periodical oscillation of flow-rate at the inlet.The numerical simulation results show that the surface wave causes oscillation of the liquid film in the swirl chamber,and then the flow oscillation occurs at the spout.Moreover,the frequency of the vortex wave is much smaller.The phase angle between the flow oscillation at spout and the pressure drop oscillation is proportional to the oscillation frequency,which agrees well with the linear injector dynamic characteristics theory.