This paper mainly studied the dynamic behaviors of bevelgeared rotor system under nonlinear oil film forces. In the bevelgeared rotor system supported on the journal bearings or squeeze film damper, oil film force is an important source of nonlinearity, which is influenced by the structural parameters of bearings, speed of rotor and the acting forces. Under the assumptions such as the rigid rotor, the gear meshing, etc. the dynamic model of bevelgeared rotor system under nonlinear oil film forces was established after considering the bevelgear relationship of the generalized displacement constraints. Because the oil film force is of strong nonlinear characteristics, its dynamic behaviors of the system, such as steadystate responses, Poincaré maps and bifurcation diagrams, were analyzed by using the numerical method. The conclusions are summarized as follows: for the unbalanced bevelgear rotor system, the rotor motions are synchronized with rotational speed at low speeds; with the increase of speed, the complicated phenomena such as the 2periodic motions in the displacement responses occur. These vibration characteristics can provide the theoretical basis for the dynamic design, structural optimization and condition monitoring.