Abstract: The wide application of digital technology has driven the Global Fourth Industrial Revolution. As the world's largest emerging economy, China has launched new infrastructure construction and accelerated the development of digital technologies such as 5G, data centers, cloud computing and the Internet of Things. Meanwhile, China faces the urgent task of carbon emission reduction. The wave of digital technology has provided an important impetus for China to achieve the goal of "carbon peak and carbon neutrality". Based on the panel data of 284 Chinese cities from 2011 to 2017, this paper constructs a comprehensive index of digital technology development from four aspects: digital infrastructure, digital factor input, digital technology-related output and digital transaction development, not only theoretically analyzes the influence mechanism of digital technology development on regional carbon emissions, but also empirically tests the overall effect of the relationship and its temporal and spatial evolution trends. In order to alleviate the possible endogenous problems, this paper takes the interaction term of the historical throughput of post and telecommunications and the annual per capita telecom revenue of each city as the instrumental variable of the digital technology development index, and constructs the two-stage least squares regression model (IV-2SLS). Then, the mediating effect model is used to test the influence paths of digital technology influencing regional carbon emissions. Considering that the three paths of the impact of digital technology on carbon emissions have different durations, the impact of digital technology on carbon emissions may have time heterogeneity. So the core explanatory variables are replaced by the digital technology development index of the current period, the first lag period and the second lag period respectively for regression. In order to further verify the spatial spillover effect of digital technology development on carbon emissions, this paper constructed the geographical distance matrix, economic distance matrix and adjacency matrix at the city level respectively, and adopted the spatial panel econometric model for spatial estimation. It is found that the development of digital technology can significantly reduce the carbon emission intensity of Chinese cities, and this conclusion is still robust through a series of robustness tests. The mechanism analysis shows that the intermediate paths of digital technology to achieve carbon emission reduction effect includes reducing energy consumption intensity, promoting industrial structure upgrading as well as improving regional technological innovation level. The spatial and temporal dynamic effect analysis shows that the carbon emission reduction effect of digital technology gradually increases with time, and digital technology can reduce the carbon emission intensity of neighboring cities through spatial spillover effect, which is conducive to the formation of coordinated regional carbon emission reduction pattern. In addition, digital technology has a significant inhibitory effect on carbon emission in eastern cities, but not in central and western cities, it can significantly reduce the carbon emission intensity of central cities, but can not play a significant inhibitory effect on carbon emission in peripheral cities. Based on the findings, we puts forward corresponding policy recommendations on improving energy efficiency of digital infrastructure, further breaking down administrative and industrial barriers, and adopting digital technology development strategies tailored to local conditions.