Abstract: Based on a certain type of aero-engine, 4-mass nonlinear dynamic model is developed for the behavior of rubbing faults in a sliding bearing-rotor-stator system, with which the synthetic effect of nonlinear reactive force and viscous shearing force of oil film and rubbing force on the response to the coupling rubbing faults of the system is analyzed. The bifurcation and chaos of the system are then analyzed via a numerical simulation with the viscous shearing force of oil film taken into account, thus revealing some practical graphic representations in the domain of actual parameters with nonlinear response for the system. It follows that when the system response occurs within a wideband frequency range it includes not only the dividing periodic motion but also the quasi-periodic motion and chaotic motion in the system, and a great number of narrow-band periodic windows are found in the chaotic motion region. The chaotic motion in the system is affected by the viscous shearing force of oil film, which should be taken into account in exploring the chaotic motion of the whole system.