Under the background of innovation driven urban development, the development of science and technology finance provides a new driving force and direction for ecological environment governance. Based on the data of 262 prefecture level cities in China from 2003 to 2018, this paper regards the implementation of "promoting the combination of science, technology and finance" as a quasi-natural experiment, and uses the Difference-in-differences (DID) method to investigate the environmental governance effect and impact mechanism of science, technology and finance policy. The results show that: firstly, the implementation of science and technology financial policy has an obvious inhibitory effect on environmental pollution, and the effect of science and technology financial policy on air pollution is more obvious than that of water pollution; Secondly, from the perspective of urban location, the effect of science, technology and financial policy on environmental governance in the eastern and northern regions is better than that in the central, Western and southern regions; From the perspective of city level, science and technology financial policy has more obvious pollution control effect for high-level cities; Finally, the intermediary effect analysis shows that financial development, technological innovation and economic scale are the effective ways for science and technology financial policy to improve the environment. In addition, the implementation of science and technology financial policy has a significant spatial spillover effect on environmental governance in adjacent areas. This paper attempts to bring environmental pollution into the evaluation framework of science, technology and financial policies for the first time, enriches and improves the relevant research on environmental governance, effectively responds to the academic debate on scientific and technological innovation, financial development and environmental governance, and provides empirical evidence for promoting high-quality economic development.