Based on the panel data of 156 prefecture level cities in China from 2006 to 2018, the national pilot policy of smart city construction in 2012 is regarded as a quasi natural experiment to test the green development effect and impact mechanism of smart city construction through psm-did method. The research results show that the national pilot smart city policy has significantly improved the green total factor productivity of Chinese cities; In terms of regional heterogeneity, compared with the central and western regions, the effect of the pilot smart city policy on the green development of cities in the eastern region is more obvious; The mechanism test shows that the pilot smart city policy generates green development effects through industrial structure and technological innovation in the whole country and the central and western regions respectively, and realizes green development through human capital and infrastructure construction in the eastern region, and accordingly puts forward policy recommendations for the construction of new smart cities in China.