National climate targets must be decomposed into key areas to guide mitigation actions. This paper presents a comparative study of China's low-carbon transition pathways at the sectoral level under the nationally determined contribution (NDC) and 2 °C targets, using the energy system model and detailed sectoral information. The results show that each sector plays different roles in terms of emission trends, mitigation potentials, technology roadmaps, investment requirements, and mitigation costs. The power sector is expected to contribute around 50% of the total mitigation. The industry sector has better cost-effective performance, with high mitigation potential and low investment requirement. By contrast, the transport and power sectors account for around 90% of total investment demand. The building and transport sectors have substantial mitigation opportunities that can be realized through technologies with negative mitigation costs. Conversely, the industry sector faces challenges in promoting carbon capture and storage, which has the highest mitigation cost. Compared with the sectoral transition pathways under the NDC target, the 2 °C scenario requires a rapid near-term decarbonization of the power sector and additional emission reductions in end-use sectors. This decarbonization is possible through comprehensive deployment of advanced low-carbon technologies as well as measures that increase investments in low-carbon infrastructure and decrease investments in fossil fuel-based technologies in the power and transport sectors. Therefore, it is important to thoroughly understand the sectoral transition pathways under different climate targets in order to coordinate inter-sectoral actions and resources in a cost-effective manner.