As the foundation of the energy internet, integrated energy system will be an important way for future energy development, and the coordinated operation of integrated energy system in the region will become crucial. Considering that the demand side natural-gas and electric energy have the same commodity properties, this paper analogizes the peak-to-valley time-of-use price strategy of electricity load. First, it sets up the mathematical model of natural-gas and electric energy peak-to-valley time-of-use price and thermal load response; second, it establishes a regional integrated energy system model with the combined electricity, heat and natural-gas supply, which takes the minimum operating system operating cost as the objective function and supply-demand balance and energy supply-storage equipment as the constraints. The example analysis shows that considering the demand side response of the electricity, heat and natural-gas is superior to not considering or considering only the single and the two responses. This can achieve lower operating costs and peak-load shifting, reduce abandoned new energy power, and improve energy utilization. This work is supported by National Natural Science Foundation of China (No. 61703144).