Given that traditional urbanization presents developing countries with the predicament of how to achieve income increase and environmental protection at the same time, the significance of smart city construction to urban sustainable development is emerging. Based on the panel data of 259 cities in China, this paper analyzes the inhibitory effect of smart city construction on pollution intensity by combining TV-DID and spatial lag models. The research conclusions show that: (1) Overall, the pollution intensity of China showed a clear downward trend from 2011 to 2019. The areas with the most serious urban pollution intensity are mainly concentrated in Shanxi Province and the northeastern provinces. (2) Smart city construction can significantly promote the pollution intensity reduction in pilot cities; At the same time, the policy also has a negative spatial spillover effect, which can promote the pollution intensity reduction of adjacent areas. Moreover, the conclusion is still robust after testing by PSM-DID, instrumental variable method, placebo test and other methods. (3) Mechanism analysis shows that smart city construction promotes the pollution intensity reduction indirectly through industrial structure upgrading. (4) The heterogeneity analysis shows that smart city construction can more effectively promote the pollution intensity reduction in China’s western cities.