Abstract: The spindle of ultra precision machine tools is generally supported by aerostatic bearings. In this paper, fitting functions between different parameters and bearing load capacity and mass inflow rate are obtained by combined Fluent software with MATLAB neural network fitting toolbox. Then the effects of different parameters on the steady characteristics of aerostatic thrust bearings are studied by the fitting functions. Firstly, the numerical pressure distribution results calculated by the Fluent in the paper are compared to experimental data in the literature published in the past to verify the correctness of the calculation model and boundary condition. Secondly, the fitting functions between bearing diameter, orifice diameter, gas film thickness, supply pressure with load capacity and mass inflow rate are obtained by using MATLAB neural network fitting toolbox. Then, the influence of the external supply structure on the pressure distribution and the effects of gas film, orifice diameter and supply pressure on the load capacity and mass inflow rate are analyzed. The results shown that the external supply structure has no significant effect on the pressure distribution and the load capacity is increased with the decreasing the film thickness, the increasing the orifice diameter and supply pressure. Moreover, the mass inflow rate is increased with the increasing the film thickness, orifice diameter and supply pressure.