Abstract: In this paper,the nonlinear responses of cracked rotor system supported on squeeze film damper (SFD) are studied.The results show that the squeeze film force can depress non synchronous response effectively and the increase of squeeze film bearing parameter can depress chaotic response.When bearing parameter is small,a certain range of rotating speed and crack depth can lead the system response to non synchronous response and the system response will become chaotic with the increase of crack depth.The system response can be fixed to stable periodic movement by increasing the damping ratio.In general case,peroid 3 movement means that the response will be chaotic.The main route for system response going to chaos is the route of intermittence to chaos and another route is from quasi periodic response to chaos.