This study, using a spring supperted complianl feil as the bearing surface, offers an evaluation of the perfomance of a gas journal bearing.The analysis is mainly concerned with the effects that the geometric and operatioral variables have to do with bearing behavior. Based on the linear theory of circular cylindrical thin shell, the formular for calculating the unit bump stiffness and the resultant stiffness of bump feil are derived . From the conception of elasto-hydrodynamic lubrication (EHL) the global Reynolds equations for bump foil journal bearings are derived . the beundary conditions in bump foil journal bearings are also proposed. Finally, by the finite-difference method, the staticcharacteristies of bump foil journal bearings with several parameters are calculated. As a result, the curves of pressure distribution,load capacity, altitude angle, minimum film thickness and frictional torque are obtained. These curves are basically in asreement with the experimental results.