Abstract: 【Objective】Based on three scales of administrative district, street and residential area,we evaluated the capacity of urban public open space social services and put forward strategies to optimize their service capacity.【Method】By using the network analysis of GIS and RS technology, the public open space(POS)in the central urban area of Nanjing was used as the research object. From the public open space service supply capacity, residents’ recreation demand and transportation channels, its social service capability was evaluated using the accessibility index. For example, C₁ the rate of service population, C₂ the ratio of service area, and C₃ public open space per capita were examined.【Result】① Supply side:the number of public open spaces in the study area was relatively small,and their distributions were unbalanced. Combined with population distribution, we showed that the service efficiency of public open space is higher in central urban areas as compared with that of marginal areas.②Demand side:combined with residential socioeconomic status(SES)study, we found that 80.15% of main urban areas had low demand for recreation areas,while marginal areas had higher demands. ③ Transportation: we examined daily travel mode of residents, and found that there is a significant difference in accessibility among various modes of transport, accessibility of motor vehicle was the best, followed by the non-motor vehicles and public transportation, and walking accessibility was the worst; only 35.13% of the residents could arrive to the nearest public open space on foot within 20 minutes. 【Conclusion】This paper evaluates the level of public open space recreation performance from the two-way point of view of supply and demand, and puts forward optimization strategies from three aspects: overall urban planning, residents’ recreation needs, and construction of the slow traffic systems. The research results can alleviate the contradiction between the lack of supply of recreational space and the surge in the demand for better living of residents, especially the intensive cities represented by Nanjing. Mean while, it also can be used for the new round Nanjing urban planning and provide reference for relevant planning practices.