In this paper a second level mathematical model for the computational simulation of the working process of a 1-kW Stirling engine has been used and the results obtained are presented. The internal circuit of the engine in the calculation scheme was divided into five chambers, namely, the expansion space, heater regenerator, cooler and the compression space, and the governing system of ordinary differential equations for the energy and mass conservation were solved in each chamber by Euler＇s method. In additional, mechanical losses in the construction of the engine have been determined and the computational results skew that the mechanical lasses for this particular design of the Stirling engine may be up to 50% of the indicated power of the engine.