Promoting green investment and green industry development is necessary to transform from the traditional crude economic model to a high-quality and high-efficiency economic model. Based on the panel data of 30 provinces in China from 2007 to 2021, this paper uses the entropy method to measure the level of sustainable development, examines the direct and spillover effects of green investment on the level of sustainable development in China through the spatial Durbin model, explores the heterogeneous characteristics of the spatial effects, and reveals the specific path of green investment to promote sustainable development in China. The level of sustainable development in China has an apparent spatial correlation: green investment can simultaneously improve the level of sustainable development in the region and nearby regions, has a prominent intermediary role in promoting the level of sustainable development in the region, has apparent heterogeneity in promoting the level of sustainable development in China, and, in the east and regions with high urbanization rates, green investment has apparent spillover effects on the level of sustainable development. There is a significant heterogeneity of green investment in promoting sustainable development in China, with green investment in eastern and highly urbanized regions having a significant spillover effect on sustainable development, i.e., green investment in eastern and highly urbanized regions can significantly promote the development of sustainable levels in neighboring regions. Recommendations: Eastern regions and regions with high urbanization rates should actively make use of their resources, location, and technological advantages to enhance the spatial spillover effect of sustainable development to lead the development of the region, gradually form a regional collaborative development trend, and drive overall sustainable development.