The goal of achieving high-quality development and meeting carbon neutrality commitments requires further innovation in green technologies. In response to this goal, the smart city policy offers a viable pathway. To test the impact of the construction of smart cities on eco-innovation, this paper conducts an empirical study based on panel data of 287 cities from 2006-2018, using a combination of double difference and propensity score matching (PSM-DID) methods, and finds that smart city construction can significantly promote eco-innovation. The mechanism test shows that smart city construction promotes eco-innovation mainly through the increase of financial expenditure on science and technology and the upgrading of industrial structure. Heterogeneity tests found that smart city construction promoted green technological innovation more significantly under area with low environmental regulation intensity, low financial development level, low export-oriented economy level and high human capital level. This paper has implications for promoting eco-innovation, creating a good ecological environment, and promoting the pilot construction of smart cities.