This study is devoted to the features of the numerical methods for the parabolic wave equation. While seeking a numerical solution, it is necessary to select a set of computational parameters of the numerical method. The choice of the computational parameters affects the speed and accuracy of the calculations. Automation of the choice of computational parameters is useful when applying mentioned numerical methods in complex software systems, where the user cannot select them manually. In this paper, we consider a finite-difference split-step Padé method for the one-way Helmholtz equation. A discrete dispersion relation based algorithm for finding the optimal computational parameters of the numerical method is presented.