In order to study the influence of external load on the stability of the rotor bearing system,the dynamic model of the rotor system of spherical hybrid sliding bearings with orifice throttling was established.The bearing lubricating mathematical model was solved,and the nonlinear oil film force was obtained.The external load on the rotor was analyzed,the Euler algorithm was used to predict the displacement,velocity and acceleration of the shaft center at the next time,and the influence of rotor system mass,unbalanced load and step load on the rotor motion trajectories was analyzed.The results show that the increase of the rotor system mass leads to the increase of the oil film force and the shaft center vibration amplitude,thereby reducing the rotary accuracy of the rotor.Compared to not considering unbalanced loads,the vibration shape is elliptical and the vibration amplitude increases after the unbalanced load is considered.Reducing the unbalance value will reduce the vibration amplitude and increase the rotary accuracy.As the step load increases,the equilibrium convergence time also increases.