Abstract: For the carbon emission peak and carbon neutrality, deep decarbonization of the energy system is imperative. The lowcarbon integrated energy system is a form of multi-energy system, which actively or passively reduces carbon emission by integrating carbon capture technologies, increasing the proportion of non-carbon energy, and fully mobilizing the flexible resources of the source-grid-load-storage. This paper reviews and prospects the key technologies of low-carbon integrated energy system planning. First, the target and path optimization methods of energy transformation are presented. Then, modeling methods of key elements in the low-carbon integrated energy system are summarized from the aspects of carbon capture and renewable energy accommodation. On this basis, according to the characteristics of different levels of low-carbon integrated energy systems, the cross-regional-level low-carbon integrated energy system planning method integrated with the carbon capture technology and highproportional clean energy, the district-level low-carbon integrated energy system planning method considering multiple types of clean energy and flexible resources, the user-level low-carbon integrated energy system planning method considering energy consumption characteristics of users and building attributes are commented, respectively. Finally, the future development challenges of low-carbon integrated energy system planning methods at different levels are prospected.