The approach and computer program based on this approach for the approximate simulation of the microwave field distribution in the complex large-scale axial structures by using the theory of geometrical optics and the wave optics are described. The main idea of the method consists in the using of the beams tracing strategy. The comparison of results with known electrodynamic systems Ansoft HFSS and CST MWS are performed. It is shown that the adoption of this method provides sufficient accuracy in the calculation of the distribution of the bulk density of electromagnetic power in the treated material.