Abstract: The transition of traditional cities to smart cities has put forward new requirements for the development of energy systems. The construction of a digitalized and interactive integrated energy system (IES) has become one of the important solutions to face the challenge. Driven by advanced information technology, the level of digitalization and informatization of IES has been constantly improving, but the realization of its technological value still needs to be explored. This paper focused on the digital twin (DT) technology of IES, analyzing the demand, value and significance of DT in the development of smart cities. Moreover, the basic framework and challenges of DT were described, and the related key technical issues were discussed. Finally, the application of DT in the stages of planning, operation, control and multi-domain collaborative interaction of IES was prospected. It is hoped that this paper could provide some ideas and references for the future development and application of the DT technology in IES.