For the flow field between the high speed motorized spindle rotor and the combined radialthrust gas bearing,the gas film 3D simulation model of combined radialthrust gas bearing was established,the numerical solution of the model was carried out by the CFD method,and the simulation results were compared with those of single radial gas bearing.The load capacity of two kinds of bearings was studied.The results show that the radial capacity and stiffness of the combined radialthrust gas bearing are lower than those of the single radial gas bearing in the static condition,only in the high speed and large eccentricity,they are close to or even over the single radial gas bearing’s.Based on theoretical analysis and simulation results,the radial capacity of the motorized spindle was tested and the test results were compared with the simulation results.The experimental curves are in good agreement with the simulation curves,and the simulation method and simulation results are verified.