Abstract: Rub-impact between the stator and rotor of a hydro turbine generator caused by electromechanical coupling oscillations, could excite bending-torsional coupling vibrations and even lead to serious safety accidents. This study has developed a bending-torsional coupling dynamic model of the rub-impact rotor system and made an analysis of the coupling vibration behaviors using numerical method, focusing on the influence of electromagnetic stiffness, mass eccentricity, and damping ratio on the vibration signals in time and frequency domains. Results show that bending and torsional electromagnetic stiffness had a coupling effect that tended to excite and amplify the vibrations, but this effect decayed as the eccentricity was increasing. When mass eccentricity was large, damping ratio had an important role because of the strong effect of bending-torsional coupling. An increase in stator radial stiffness leaded to weaker bending vibrations but stronger torsional vibrations. The results would be useful to the design, control and diagnosis of rotor systems and their economical operation.