With the advancement of global urbanization, under-bridge spaces in cities often become idle gray areas. In Donghu District, Nanchang, where Bayi Bridge is located, faced a severe aging problem, and the under-bridge space has become an important social and activity venue for surrounding elderly residents. This study conducts multidimensional research on the space under the Bayi Bridge through site analysis, questionnaire survey, ENVI-met microclimate simulation, and case references. The questionnaire survey shows that the elderly’s main needs focus on infrastructure such as seating and toilet, as well as activities like chess and light exercise, while the existing community elderly services are severely insufficient.