In the context of combating climate change and pursuing sustainable economic development, technological innovation is considered to be an important engine for promoting the green transformation of the economy and achieving sustainable development. This study investigates the impact of technological innovation on the carbon intensity of Chinese cities using a spatial Durbin model combined with prefecture-level data. Through a standard spatial econometric analysis, this paper reveals the spatial relationship between the innovation and carbon emission, which exceeds the maximum explanatory power of linear regression. The results of empirical analysis show that: (1) overall, the improvement of technological innovation level in China has a negative spatial spillover effect on the carbon emission intensity of cities, which can reduce the carbon emission intensity of the city and the neighboring cities; (2) from a geographical perspective, the spatial spillover effect of the level of technological innovation on the carbon emission intensity of cities in western China is not significant compared with cities in other regions; (3) the spatial spillover effect of the improvement of technological innovation on the carbon emission intensity of non-resource-based cities is more significant than that of resource-based cities. Therefore, we need to increase investment in technological innovation and optimize the industrial structure. At the same time, we need to fully utilize the spatial spillover effect to help cities achieve synergistic carbon reduction.