Green Electricity Certificates (GECs) serve as the sole official documentation of the environmental attributes of renewable energy generation in China. Their trading has become a crucial market-based mechanism for facilitating China’s energy transition. The Green Electricity Certificate trading system enables the quantification and tradability of the environmental value of renewable energy electricity, driving its transformation from a purely physical electricity commodity into one with dual attributes encompassing both power and environmental value. Currently, China has basically formed an institutional framework with the Energy Law of the People’s Republic of China as the fundamental legal basis, multi-level policy documents as the core support, and standard technical specifications as the implementation safeguard. However, multiple challenges still exist in aspects such as the construction of the legal and regulatory system, the definition of the legal attributes of GECs, and the realization of environmental value. In view of this, China’s Green Electricity Certificate trading system can be improved from four dimensions: the legal and regulatory system, the realization of environmental rights and interests, the trading mechanism, and alignment with international practices.