The analysis of the impact of smart city pilots on energy efficiency is the key to achieving both urban smart and green development, and it is also a major issue that needs attention to realize the green transformation of production and lifestyle. This paper regards China’s smart city pilot policy as a quasi-natural experiment. It uses the progressive difference in differences method to systematically evaluate the effect of urban digitalization and intelligent development on the improvement of energy efficiency, and combines the propensity score matching method and the instrumental variable method to further proceed verification. The paper conclusions show that: Smart city construction improves the energy efficiency of pilot cities by about 8.41% per year, and innovation is one of its mechanisms; There is a time lag in the energy efficiency improvement effect of the construction of a smart city, and it continues to decay in the later period, which does not have a positive radiation effect on the energy efficiency of its surrounding cities；The energy efficiency of non-eastern region and cities with larger populations has increased significantly in the construction of smart city; While improving energy efficiency, the construction of smart city has not further enhanced the city energy rebound effect.