The intensification of the greenhouse effect has led to a gradual increase in people's awareness of carbon capture. Aiming at the carbon capture problem, combining the CO ₂ supercritical Rankine cycle with the organic Rankine cycle, the original gas turbine exhaust gas power generation system was improved,an LNG cold energy cascade utilization system combining exhaust gas power generation and CO ₂ capture was proposed. The thermodynamic simulation of the system was carried out using Aspen Plus software, the effects of evaporation pressure and evaporation temperature on the thermodynamic performance of the system were analyzed in detail. The results show that the increasing of the evaporation pressure and evaporation temperature of the CO ₂ supercritical Rankine cycle have a positive effect on the net output power and thermal efficiency of the system. After the evaporation temperature of the organic Rankine cycle reaches 250 ℃, the waste heat recovery rate reaches the maximum value and no longer changes with evaporation pressure. The net output power of the system can reach 251.6 kW, the recovery rate of waste heat is 92.00% and the exergy efficiency is 57.00%.The amount of CO ₂ liquefaction can reach 883.6 kg/h, which is equivalent to reducing CO ₂ emissions by 7.63 million tons per year, and is of great significance to environmental protection.