Digital infrastructure construction provides conditions for the green utilization efficiency of urban land. Taking the construction of the Broadband China demonstration cities carried out in three batches as a quasi-natural experiment, this paper uses the panel data of 283 Chinese cities from 2004 to 2021. Through the spatial Durbin difference-in-differences model and the spatial mediation effect model, an empirical test is conducted on the mechanism and spatial spillover effect of digital infrastructure construction on the green utilization efficiency of urban land. The results show that the digital infrastructure construction in pilot cities has significant local empowering effects and spatial spillover effects on the green utilization efficiency of land, and the spatial spillover effects are greater than the local empowering effects. The “policy dividends” spilling over to neighboring cities have a greater impact on non-pilot cities than on pilot cities; digital infrastructure construction empowers the green utilization efficiency of land in the local city and neighboring cities by increasing the stock of green technology and enhancing the level of government supervision; the empowering effect of digital infrastructure construction on the green utilization efficiency of urban land is more significant in cities with low resource allocation efficiency, small terrain undulations, and low levels of transportation infrastructure. Therefore, some countermeasures and suggestions are proposed, including improving government support for green technology innovation, constructing a multi-subject cooperative supervision model for green land use, and promoting digital infrastructure development in accordance with local conditions. The research results provide a reference for strengthening the construction of Digital China and promoting the green transformation of urban land use patterns.