Abstract: In view of general equations of externally pressurized gas lubrication in dimensionless form,coupling boundary conditions of externally pressurized spherical gas bearing and characteristics of non-steady Reynolds' equations were analyzed particularly.Similitude criteria for steady operation and non-steady operation of externally pressurized spherical gas bearing with inherent compensation were deduced,which may be considered a corrected form to the similitude criteria of hydrodynamic gas bearing put forward by V.N.Constantinescu.Computation results was surely in agreement with analyzed conclusion of similitude theory and two spherical gas bearing only with different radius should operate similarly with other parameters retain fixed.Influence to bearing's static and dynamic characteristics can be estimated by similitude criteria due to changes of sphere radius.