At present, China is facing development challenges such as the red line of arable land, resource shortage, and tightening ecological and environmental constraints. In this context, improving the land green utilization efficiency is not only an important deployment to optimize the spatial layout of the country and improve resource carrying capacity, but also an inevitable choice for the comprehensive green transformation of economic and social development. The digital infrastructure represented by the “Broadband China” strategy, as the strategic cornerstone of the development of new economic formats such as the digital economy, will not only greatly promote the development of digital infrastructure in pilot areas, but may also have a profound impact on their land use status. Therefore, whether there is an inherent connection between digital infrastructure construction and land green utilization efficiency has become an important question that urgently needs to be answered. However, there is currently no literature exploring the relationship and underlying mechanisms between the two. Based on theoretical analysis, this paper uses panel data from 282 prefecture-level and above cities in China from 2006 to 2020 to examine the “Broadband China” strategy as a quasi-natural experiment. It uses a progressive double difference model to examine the impact, intrinsic mechanisms, and spatial spillover effects of digital infrastructure construction on land green utilization efficiency. The heterogeneity and promotion effects of this policy are also explored. The results show that: (1) The “Broadband China” strategy can significantly improve the urban land green utilization efficiency, and this impact exhibits long-term, cumulative, and short-term lag characteristics; (2) Promoting green technology innovation and upgrading industrial structure are the internal mechanisms for improving land green utilization efficiency in the “Broadband China” strategy; (3) The “Broadband China” strategy has a significant spatial spillover effect on improving the urban land green utilization efficiency; (4) The positive impact of the “Broadband China” strategy on land green utilization efficiency is more evident in eastern regions, large-scale cities, and non-resource-based cities; (5) With the expansion of the pilot areas of “Broadband China”, this policy shows promotion effects. Compared with previous studies, this paper's marginal contributions lie in: Firstly, in terms of the research perspective, this study adopts the “Broadband China” strategy as a quasi-natural experiment to examine the impact effects of digital infrastructure development on land green utilization efficiency. The study aims to reveal the underlying mechanisms through two major channels: green technological innovation and industrial structure upgrading, and then delve into the analysis of its spatial spillover effects; Secondly, in terms of content depth, considering the potential heterogeneity effects of the “Broadband China” strategy and the fact of its phased implementation, this study explores its heterogeneous manifestations based on three dimensions: urban location, scale, and type, and evaluates its promotion effects. This study not only contributes to enriching and expanding relevant research on the effects of the “Broadband China” strategy but also provides a certain path support and decision basis for the continuous and efficient promotion of this policy and the improvement of urban land green utilization efficiency. To a certain extent, this paper reveals the inherent logic of how digital infrastructure construction affects the land green utilization efficiency, which helps the government actively and steadily promote the “Broadband China” strategy, emphasize the role of green technological innovation and industrial structure upgrading, and consider the geographical and economic connections between regions in the development process. It provides a reference for cities to seize the opportunity of using digital infrastructure construction to improve land green utilization efficiency and promote the comprehensive green transformation of economic and social development.