The nonlinear governing equations of motion with high dimensional DOF are established for an aero engine rotorbearing system based on finite element method, in which the nonlinear force of the rolling bearing, the shear deformation, gyroscopic moment and moment of inertia of the rotor are taken into account. The adaptive step Newmarkβ algorithm is employed to analyze the unbalance response of the rotor at various rotating speeds. The effect of unbalance and clearance of the bearing on the amplitude of VC(Varying Compliance) vibration is obtained. The results show that the amplitude of VC vibration decreases at first with the increasing of rotating speed. As the rotating speed is further increased, the amplitude begins to increase and then decreases again until it disappears. The amplitude of VC vibration increases while the clearance of the bearing is increased. However, the amplitude of VC vibration is insensitive to the change of unbalance.