Energy sector decarbonization is a key battleground in China’s march toward carbon neutrality, and understanding what it means and takes is crucial for its policy-making and sustainable implementation. Here we analyze the structural challenges and review the necessary supporting technologies and systems of energy sector decarbonization in China. It requires not only supporting technologies such as energy efficiency, zero-carbon energy, and carbon capture, utilization and storage, but also enabling systems such as the transmission, distribution and storage system, carbon governance mechanisms, and risk alleviation systems addressing risks of renewables waste and critical mineral supply. A technology roadmap highlighting techno-economics, environmental impact, technology innovation, and carbon market mechanisms is needed to facilitate energy sector decarbonization in China.