Abstract: Vibration characteristics of a rub impact rotor system supported on oil film bearings were investigated.Elastic impact and the Coulomb type of frictional relationship was assumed.Rotating speed and the system damping were used as control parameters to discover routes to and out of chaos and to study various forms of periodic、quasi-periodic and chaotic vibrations.Very rich types of chaotic vibrations were found for the model discussed.Also the system motion shows two different forms of intermittent phenomena.One is the interchange between periodic and quasi-periodic vibrations.Another is between periodic and chaotic vibrations.Vibration features such as chaotic vibration,intermittent phenomena and broad-band of periodic vibration can be effectively used to diagnose the rub impact fault which often happens in a rotor system.