The emergence of a new but extremely important branch of modern industry, the powder metallurgy industry in today's world is increasingly emerging as a necessity due to its speed of manufacturing individual components. Sintered metal products obtained by powder metallurgy have been successfully replacing those obtained by more classical methods such as casting or forging steel for many years. This is primarily due to a significant reduction in production costs, manufacturing accuracy, surface smoothness, etc. This thesis describes the elasto-plastic deformation of the microstructure of sintered steel Astaloy Mo + 0.2C. In order to make the process of obtaining the necessary models for describing the deformation of the microstructure as short as possible, we defined the minimum required model size. Direct numerical simulation on representative volume elements was applied, but before the analyzes were performed, the theoretical background was given to describe the problem of deformation of sintered steel in the elasto-plastic region. The elasto-plastic deformation region was described using the Ramberg-Osgood approach using the finite element method using the Abaqus software package. A study of the influence of the size of the RVE model on the mechanical behavior of sintered steel Astaloy Mo + 0.2C was performed. The performed numerical analyzes were verified by comparison with the results obtained using numerical simulations based on the phase field method. Finally, this thesis presents a methodology for calibration of material parameters of elasticity and plasticity for numerical material models for the implementation of numerical simulations at the macro- and micro-level based on the comparison of numerical results with experimental results obtained by tensile test. The microstructure of the material has been shown to influence the results of numerical analyzes and some guidelines for improving the applied methodology have been proposed.