Abstract An actuator system (gas-hydrate engine) using the dissociation and recombined continuous cycle of CO 2 gas hydrate was developed. The heat source temperatures required for the operation of the proposed system are in the temperature range of green energy and low-quality exhaust heat. The energy flow of this proposed system was investigated by numerical analysis. From these results, for example, the entrance operating conditions of the recombination equipment are 9 °C and 1.2 MPa, and the exit conditions are 0 °C and 5 MPa. In the case of a heat source temperature of 20 °C of the recombination equipment, a heat source temperature of −5 °C of the dissociation equipment and the passing of a working fluid comprised of 1150 g/s of CO 2 and H 2O about 5 kW of electric power can be obtained. Moreover, although the recombined speed was remarkably slow compared with dissociation, this study considered the relation of recombined speed between the physical conditions of the working fluid and the volume of the recombination equipment. Based on the results obtained in this study, a prototype will be developed next.