This paper attempts to study the lubrication property of a hydrodynamic journal bearing under transient loads.Nonlinear equations of motion for the rotor-bearing system considering the journal inertia effects were established.Acomputational method using the Euler scheme was put forward to determine the transient journal centre trajectories of the bearing.Three kinds of dynamic loads were imposed on the shaft:step loads,rectangular pulse loads and sinusoidal impulse loads.The laws of the journal centre trajectories,the maximum film pressure and the minimum film thickness varying with the loads were obtained.The results show that under the transient transient loads,the centre trajectories,the maximum film pressure and the minimum film thickness change in large ranges with a certain degree of oscillation process.Asthe time-limited pulse load attenuates the journal center trajectory converges on the original equilibrium position,while the step load makes the journal center converge on a new equilibrium position.