The current method used for the expansion planning of the distribution network in a regional integrated energy system overlooks the analysis of the structure and operational characteristics of various systems within the integrated energy system. This oversight results in high pollutant emissions, electricity consumption, and gas consumption in the planned distribution network. Aiming at the regional integrated energy system, a planning method for distribution network expansion is proposed. Firstly, the structure of the regional integrated energy system is analyzed while models for heating, cooling, and power supply are constructed. Next, a two?tier optimization model is established where the upper?level model aims to minimize the overall planning cost, and the lower?level model aims to maximize energy utilization efficiency. The upper and lower?tier models can respectively extend the planning of the system distribution network and optimize the regional integrated energy system. The simulation results of a distribution network connected to a regional integrated energy system show that the proposed method results in a reduction of distribution network loss rate to 4%~5%, the load balancing rate reaching more than 90%, and significantly controlled consumption of electricity, gas, pollutant discharge and load power after planning