It is very difficult to acquire the exact solution of Reynolds equation when solving aerostatic lubrication problem. In order to improve the design accuracy of axial bearing system for aerostatic spindle, the mathematics model of aerostatic thrust bearing with orifice compensated was established. Reynolds equation in cylindrical coordinate was discretized based on the finite element method. A numerical simulation software was developed to solve the pressure equations and static characteristics of aerostatic thrust bearing in the super relaxation iteration method on the basis of MATLAB7.0 tools. Taking axial double thrust bearings of a aerostatic spindle as an example, the pressure distribution of gas film were obtained by numerical simulation, and static characteristics at different feedhole diameter and gas supply pressure were also obtained. The structure parameters and operation parameter were optimized in order to maximize the stiffness of the gas bearing, and the static characteristics of the double thrust bearings were educed.