Abstract: Based on fast Fourial transform (FFT), a method of the equivalent spatial frequency transmission has been proposed and applied to calculate resonator modes of the axis-asymmetric positive confocal resonators with a one-dimensional variable reflectivity mirror (1D VRM) used for slab lasers, which have been then compared with the results of the axis- asymmetric positive confocal resonator with a uniform reflectivity mirror (URM), and with a two-dimensional rotationally-symmetrical variable reflectivity mirror (2D VRM), respectively. In our calculations the resonator axis-asymmetry and gain saturation characteristics of the active medium have been considered. Numerical calculation results have demonstrated that the 1D VRM axis-asymmetric positive confocal resonator has the advantage of provid