To enhance the applicability of stereoscopic greening technology for the renovation of existing public buildings in high-density mountainous urban areas, this study conducted on-site investigations in a typical high-density mountainous urban area of Chongqing. This study collected data on the application of vertical greening technology in urban public buildings and analyzed the suitability of various vertical greening technologies for the renovation of public buildings. The results indicate that modular vertical greening is currently more suitable for the renovation of public buildings in such cities; however, further optimization is needed in terms of the overall compatibility, stability of modular units, and adaptability of modular plants to the local environment. This study can provide a theoretical basis for the feasibility of adopting vertical greening retrofitting for public buildings in high-density mountainous cities, and provide a reference for the planning and sustainable development of such cities.