Based on sample data from 273 prefecture-level cities between 2015 and 2022, this study utilizes key digital technology patent data to measure the level of digital technology innovation. It comprehensively considers the dynamic interaction effects between “pollution reduction” and “carbon reduction,” and calculates the synergistic effect of pollution reduction and carbon reduction from a performance perspective to represent the level of urban green development. The impact mechanism of digital technology innovation on the level of green development in cities is examined from three aspects: energy structure, industrial structure, and the level of digital and intelligent integration. Heterogeneity analysis is conducted based on city type, policy pilot status, and geographical location. The findings are as follows: ① Digital technology innovation has a significant positive impact on the level of green development in cities. ② Digital technology innovation influences the level of green development in cities mainly by optimizing energy structures, promoting industrial structure upgrades, and driving digital and intelligent integration in cities. ③ Based on heterogeneity analysis conducted by city type, policy pilot status, and geographical location, digital technology innovation significantly enhances the level of green development in resource-based cities, key cities for air pollution prevention and control, non-low-carbon city pilots, smart city pilots, as well as cities in western and northeastern regions. To fully leverage the promotional effects of digital technology innovation on the level of green development in cities, and to drive comprehensive green transformation in both the economy and society through digital technology innovation, the following key areas should be focused on: strengthening investment in digital technology innovation to expand the pathways for synergistically advancing pollution reduction and carbon emission decrease; enhancing the application of digital technology to reshape the energy structure; deepening the integration of digital technology with the real economy to facilitate the upgrading of industrial structures; intensifying the integration of digital intelligence with urban development to promote the construction of smart cities; and implementing differentiated regional policies in combination with geographical location characteristics.