In recent years, the replacement of retired coal-fired power plants with nuclear power plants (also known as coal-to-nuclear conversion, C2N) has been considered a particularly cost-effective solution for power system decarbonization amid global climate change mitigation goals. In this study, we improved a power system model of China equipped with provincial spatial resolution. Specifically, we expanded the classification of nuclear technologies from one to four types, based on generation and reactor design, and incorporated relevant C2N conversion constraints. This improvement allows quantification of C2N’s potential role in decarbonizing China’s power system, following the identification of its maximum conversion potential. The results indicate that by utilizing conventional site resources in both coastal and inland China, a major growth of nuclear capacity is possible under China’s carbon peaking and neutrality goals, reaching 422 GW by 2060, with 42% of this capacity being small modular reactors that offer greater operational flexibility. In 2060, nuclear power will become an important source of electricity generation in China, accounting for 18% of total supply. Site resource availability represents a major constraint to this development: Expanding site availability through C2N has the potential to further increase nuclear capacity in 2060 by 13%-23%, while raising nuclear’s share of total electricity supply that year by 2-4 percentage points. Expanding nuclear energy’s share in China’s decarbonization via C2N will yield cost savings of 0.22%-0.69% of system cost from 2030 to 2060.