The invention discloses a fault diagnosis method of abnormal vibration, of a rotor, caused by a floating oil retainer. The fault diagnosis method of abnormal vibration, of a rotor, caused by a floating oil retainer includes the steps: importing shafting TSI data into a fault diagnosis system; setting a threshold, utilizing a spectrum analysis method, determining whether the property of shafting abnormity vibration belongs to common forced vibration, extracting typical characteristics of a fault, analyzing operating parameters of a set, and eliminating the influence of load, thermal deformation and field current; and with combination of shafting structure analysis structure, determining whether abnormal vibration of the rotor is caused by a floating oil retainer, and then obtaining a diagnosis result. The fault diagnosis method of abnormal vibration, of a rotor, caused by a floating oil retainer has the advantages of being comprehensive in the considered extracted characteristics, being suitable for field fault diagnosis, being quick and accurate in result diagnosis, and having practicality and operability.