Abstract: Under the background of urban renewal, intergenerational spatial justice in old communities has become increasingly prominent. Existing studies, however, mainly focus on explicit inequalities in resource allocation while overlooking their implicit mechanisms. Taking Wanshoucun Community, Nanjing City, Jiangsu Province as a case, this study develops a four-dimensional evaluation framework (distribution, function, participation, environment) and employs questionnaire surveys, behavioral analysis, and the Analytic Hierarchy Process (AHP) to measure intergenerational justice in public space experience. Results reveal a reversed hierarchy of justice levels: middleaged > elderly > young adults, with young adults scoring the lowest overall, challenging the conventional assumption that the elderly are necessarily the most disadvantaged group. The disadvantages faced by young adults stem not from explicit resource shortages, but from an 'implicit intergenerational imbalance' shaped by functional mismatch, participatory exclusion, and environmental disparity. The study highlights the independent explanatory power of the intergenerational dimension in spatial justice theory and proposes a shift in old-community renewal from 'compensating vulnerable groups' toward 'structural reconfiguration'.