The paper reports on the results of numerical simulation of disk-shaped dummy load for L-S band microwave calorimeter in a metal case. We have used the finite element method as a solution tool for Maxwell's equations in 2Daxisymmetric case in the frequency domain. As a result of the calculations the reflection coefficient of the TM 01 electromagnetic wave from the dummy load at normal incidence was obtained. Also we have obtained the coefficient of dielectric losses of electromagnetic radiation in the dummy load's entrance window made of different materials. Current results confirm and improve the theoretical estimations of the optimal parameters previously obtained in the simplified two-dimensional model.