On the basis of liquid cavitation two-phase flow theory of hydrodynamic lubrication,the hydrodynamic lubrication model of the step thrust bearing is analyzed by means of computational fluid dynamics（ CFD） simulation,which is based on the numerical solution of the Navier-Stokes. The effects of depth ratio,length ratio,number of steps and rotate speed on the load capacity of the step bearing is investigated. The results of the study indicate that the influences of depth ratio on the load capacity is more dramatically than the length ratio. The depth ratio is 1. 7,and the length ratio is 1. 3,the load capacity is largest. When the rotate speed increases,the load capacity grows linearly. The load capacity increases at first and decreases afterwards with the increasing of the number of steps.