Abstract: A term has been suggested to add to conventional Reynolds equation so as to avoid the noise and errors from finding the pressure gradient to satisfy the mass flow rate condition. The different forms of Reynolds equations in different coordinate systems are deduced into one form. Two methods of equation discretization, namely the Weighted Residual Method and Optimization of Variation Fuctionals have been analyzed. The cause leading to divergence in numerical calculation of thin gas film has been explored and the countermeasure to get rid of the divergence been suggested. As the results, the method is applicable to analysis and calculation of the lubrication of various externally pressurized bearings.