Abstract: From perspective of rotor dynamics, a discretized dynamic equation for rotor was established by combining the D'Alembert principle and transfer matrix method．Based on theory of hydrodynamic bearings and finite difference method for calculating nonlinear oil film pressure, a dynamic model of multi axis centrifugal compression device rotor system supported by sliding bearings was proposed．The imbalance effect and vibration characteristics of nonlinear bearing rotor system were analyzed from aspects of axis trajectory, bearing eccentricity, and spectral response．Results indicated that vibration characteristics of rotor under idealized imbalance were mainly manifested as subsynchronous vortices．As imbalance increased, main synchronous response of rotor increased．Under an imbalance of 0.2 g·mm, rotor system exhibited multiple elliptical trajectories, which was very detrimental to service life of rotor system．Under G1 balance accuracy, rotor system had good dynamic characteristics, which could ensure stable and healthy operation of multi axis compression device spindle rotor system under normal working conditions．