The integrated energy system (IES), as an energy integration system that expands energy from electricity to gas, heat, and cold systems, has become an important part of the Energy Internet. Aiming at the perspective of user demand-side load control, the optimization operation of the integrated energy system was studied, and a two-stage optimal scheduling model for IES was established. In the first stage, the user’s demand response model was established by combining various shiftable loads and the thermal energy storage of buildings, and considering the air conditioner as the user’s electro-thermal coupling device. In the second stage, a mixed-integer linear model that optimizes the operation of the IES with the lowest operating cost is established, and the output of each device of the system is optimized using the solver. Finally, the effectiveness of the proposed model and algorithm is verified by simulation analysis.