Abstract:Global warming has a great impact on the environment and economic development. Carbon emissions are the main cause of climate warming. Carbon trading policy is a core policy tool to control carbon emissions based on market mechanism and promote green and low-carbon development. By using the panel data of 30 provinces in China from 2004 to 2019, the emission reduction effect and its mechanism of carbon trading policy are empirically studied based on the double difference and mediating effect model. The results show that carbon trading policy has significant emission reduction effect both in general and in sub regions, but there are regional differences in the size of the effect. The emission reduction effect of carbon trading policy in the eastern region is greater than that in the central and western regions. Mechanism analysis shows that carbon trading policy can reduce emissions through reducing the scale of energy consumption, promoting technological innovation, promoting the upgrading of industrial structure and increasing foreign direct investment. Energy scale, technological innovation, industrial structure and foreign investment have significant mediating effects in the transmission of carbon trading policy, but there are regional differences in this transmission mechanism.