Based on the core concept of low-carbon leadership，this paper established a low-carbon leadership assessment index system and its assessment method，and calculated the data of G20. The assessment results show that，EU is still a significant force leading global low-carbon development，and China，as an important contributor in international climate governance，can play a greater leading role. A series of policies adopted by US Trump administration in climate change issue，greatly weaken its leading position in international climate governance. In the end of this paper，shortages and improvement direction of this assessment index system were discussed.