Using a simple computer model, the properties of a Stirling engine are studied, where the working substanceis a chemically reacting gas with a reversible reaction CO + 2H2  CH3OH. The model takes into accountthe relaxation time of hydrodynamic processes in the regenerator. In this case, the engine is considered toconsist of three main parts: a heater, regenerator and a cooler, this is fundamental difference from theLanglois Justin model proposed in 2006. The pressure in the engine is 20 MPa, the working piston is free.The efficiency is compared for two cases: 1) a reversible chemical reaction occurs in the working gas and2) the working gas is chemically inert with relatively high and low molar mass. The average power over theoscillation period is several hundred watts, but the maximum power can reach 2 kW. To increase the powerof an engine with reversible chemical reaction, it is necessary to increase the volume of the cooler and reducethe volume of the heater. The modeling results are in good agreement with the previously obtained theoreticalresults of one of the authors (K. Sabdenov, 2023) based on the analysis of the Stirling cycle with reversiblechemical reaction.