A rub-impact model of nonlinear rotor system is built.Based on the model and using numerical calculation,the responses of nonlinear rub-impact rotor systems,such as period-one motions,sub-harmonic and super-harmonic vibrations,quasi-periodic motions and chaotic motions,are investigated.Nonlinear vibration characteristics of a rub-impact rotor revealed in this paper are of great significance to the condition monitoring and diagnostics of the rotor system.