Abstract: Based on the analysis of the discrete model, an FEM-based model of rotor-bearing system was developed considering some important influencing factors other than the nonlinear factors of the bearing, such as the inertia distribution, shear, transverse torsion, structural geometric parameters of the system. The dynamic behavior of the system and discrete system was discussed separately and comparatively on the same unbalance conditions, and the results showed that the dynamic behavior as expressed in the two models is different to a certain extent because of the increased influencing factors taken into account. The FEM model regarded as superior in design parameters, and it can provide more convincible data for the nonlinear characteristics of a rotor system, thus giving more accurate reference and verification to the nonlinearly dynamic design of the complex rotor system.