Abstract: The dynamical behaviors of a flexible rotor-fluid film bearing system with squeeze film damper are investigated.Owing to the nonlinearity of the film forces, there are many complex phenomena in the system,such as:jump,nonsynchronous motion etc.As the parameters are varied,the system can undergo a series of bifurcations.It is found that the secondary Hopf bifurcation,a series of period-doubling bifurcation and the saddle-node bifurcation result in quasi-periodic motion,subharmonic adoption motion and jump phenomenon respectively.The results of this study show that the introduction of squeeze film dampers in this system may lead to undesirable nonsynchronous vibrations.