In order to solve the problem that the dynamic characteristics and load control strategy of supercritical CO2 waste heat utilization system under the load fluctuation of power grid caused by large-scale grid connection of new energy. Supercritical CO2 waste heat utilization system consisting of supercritical CO2 Brayton cycle and transcritical CO2 cycle as a gas turbine bottom cycle is considered as one of the important technological routes to enhance the large-scale consumption of renewable energy. An in-depth study of the dynamic characteristics of the supercritical CO2 waste heat utilization system is an important basis for enhancing the efficient and flexible operation of the system. This chapter takes the supercritical CO2 waste heat utilization system as an object, and uses the gas turbine exhaust parameter under the regulation of IGV control strategy as a heat source, constructs a dynamic simulation model in Matlab/Simulink, and carries out dynamic simulation calculations. The results show that, as the combustion engine is reduced from full load to 90%, 80%, and 70%, the combustion engine exhaust temperature stabilization time is reduced from 4.8 to 3.83 s, the top-cycle temperature drop decreases when the unit load is reduced, the temperature of the transcritical bottom-cycle fluctuates less due to the influence of thermal inertia, the mass flow rates of the bottom-cycle and the bottom-cycle output power are strongly coupled, and the total efficiency of the system decreases with the reduction of combustion engine load. When the combustion engine load is reduced to 70%, the total efficiency of the system is 27.08%, at this time, the supercritical CO2 waste heat recovery system to recover the waste heat of the combustion engine still has high efficiency and economy. The results of the study provide a reference for the actual recovery of combustion engine waste heat by supercritical CO2 waste heat recovery system.