Abstract: A composite supercritical carbon dioxide-organic Rankine combined cycle was used for waste heat recovery from the gas turbine, comprehensive thermodynamic and exergy economic model was established, and the impact of key parameters on the performance of the combined cycle system was explored. A study has been carried out on the combined cycle system from multiple purposes such as thermodynamic performance, space compactness and exergy economic performance, so as to conduct the multi-objective optimization on the combined cycle. Results show that the combined cycle efficiency in the optimal state can reach 54.56%, which is 4.2% higher than that of the conventional gas turbine-steam combined cycle. The required heat exchange area per unit power output is 0.117 8 m²/kW, which is 21.41% lower than that of the conventional gas turbine-steam combined cycle.