The non-ideal cylindrical surface model based on profile measurement was built by using Geomagic Studio software, and it was imported into UG12.0 to create the aerostatic bearing simulation model, which can be simulated by using ANSYS WORKBENCH software. Ten groups of rotors and porous aerostatic bearings were selected as experimental objects, and the bearing capacities and stiffness values of the aerostatic spindles based on non-ideal cylindrical surfaces and global sizes were simulated and analyzed respectively. The bearing capacities and stiffness values of the aerostatic spindles above were measured on the modular tester of spindle’s comprehensive performances. Simulation and test results showed that among three global sizes, the bearing capacities of the gas films formed by the non-ideal cylindrical surfaces of rotors and bearings are closed to that of the gas films formed by two ideal cylindrical surfaces of rotors with least-squares diameters, and the stiffness values of gas films formed two non-ideal cylindrical surfaces are closer to their corresponding test results. Therefore, so the modeling method of the gas film based on two non-ideal cylindrical surfaces is more suitable for the stiffness evaluation of the aerostatic spindle.