The core components of an urban green space system are affiliated green spaces, whose openness and shared nature constitute essential strategies for developing Park City. This study focuses on Xinzhuang Town in the Minhang District of Shanghai as a case study, examining the relationship between the supply and demand of regional public green spaces. It identifies areas within the case study where supply is lacking and, through field research, reveals affiliated green spaces in those areas that have the potential to be opened up. By considering two dimensions, landscape function and spatial layout, the study identifies key indicators for assessing the potential of these affiliated green spaces and conducts a thorough evaluation of 36 such spaces in the low-supply areas of Xinzhuang Town. Based on the evaluation results, the study investigates the supplementary effects of highly accessible affiliated green spaces on the regional green space supply and demand dynamics. The research indicates that opening affiliated green spaces significantly improves the supply and demand situation in certain areas. Areas that remain undeveloped can further enhance the potential and value of affiliated green spaces through improved management strategies, targeted planning and design, and a maintenance model that encourages diverse participation, offering valuable insights and inspiration for the development of affiliated green spaces in high-density urban environments.