Abstract: The linear relationship between the corrected value and measured value is used to balance the rotor in the influence coefficient method.When rotor are supported on the bearings having nonlinear stiffness characteristics,it would be difficult to balance the rotors since linear hypothesis would not be valid.The motion equation of a multiple-degree rotor system is formulated by using Lagrange equation and flexibility influence coefficients.The equivalent linearization model of the nonlinear multiple-degree system is used to balance the nonlinear system in this paper.The example shows that the vibration response caused by unbalance mass reduces greatly and the method developed in this paper is successful.