Objective  The urban park system is the material carrier of Park City construction. The urban development model centering on Park City puts forward higher requirements for the optimization of the structure and management innovation of the urban park system. The planning of the urban park system has long been based on the goal of spatial layout and construction to meet the increasing demands of people for ecological environment and high-quality living environment, and has been focusing on the upgrade of hierarchical arrangement and comprehensive service functions. However, in the construction of the urban park system, the emphasis on quantity rather than actual benefits has led to increasingly prominent problems such as supply-demand imbalance and low efficiency. The network structure of the urban park system is in urgent need of optimization.

Methods  In terms of technical methods, domestic and foreign scholars have adopted such methods as fractal theory, GIS network analysis and spatial syntax to conduct static evaluation and analysis of park space structure, which has promoted the optimization and improvement of spatial layout and spatial structure of urban parks. However, the current research on urban park systems is mainly based on the superposition of individual park attributes to build networks, lacking analysis of the interaction between parks, especially lacking consideration of the service capacity of urban parks under the influence of residents’ activities. The social network analysis method selects the “supply − demand” relationship between parks and urban residents to construct a social network model of urban park systems based on “human − ecology” relationship, identifies the importance of individual parks in the network structure of parks and the stability of the overall structure. On the other hand, social network analysis emphasizes the spatial mismatch between supply and demand and fair benefits from the human perspective, which can directly touch the essence of network structure relationships. Taking Shanghai as an example, the research adopts social network analysis to analyze and evaluate the urban park system. The construction of the Shanghai urban park social network model is based on the service relationship between urban parks and residential areas. The centrality index of network nodes evaluates the importance of network nodes and the hierarchical structure of the network. Specific centrality indicators include degree centrality and betweenness centrality. Moreover, the research adopts the UCINET software to calculate the degree centrality, betweenness centrality, and comprehensive node importance of each park, and adopts Netdraw to draw the network topology structure. The research also analyzes the position of each park node in the urban park network through spatial visualization in ArcGIS.

Results  Firstly, the spatial distribution of important network nodes in Shanghai’s urban parks is characterized by central aggregation distribution. Highly important parks are concentrated in the central urban area of Shanghai, especially the early developed Puxi District. Suburban parks are intermediate hubs in the network and can help residents quickly obtain the service functions of different types of parks. Parks in the outer suburbs are not that important. The research finds that the importance of park nodes is closely related to the degree and betweenness centrality of parks, which represent the influence and connectivity of parks. Relevant factors influencing the importance of park nodes are hereby detailed as follows. 1) Attractiveness of parks. High-quality parks can attract residents from long distances to visit, increasing the frequency and volume of park visits and enhancing the influence and importance of parks. 2) Spatial links between parks and residential areas. The larger the service area of a park, the more services it can provide to residents. The more prominent the synergistic role of a park in connecting other parks and ensuring residents’ use of urban parks, the more obvious the “intermediary” role and the higher the irreplaceability of the park.

Conclusion  The construction of the park system should not only consider the comprehensiveness of park scale, location, and type, but also take into account the supply and demand relationship of urban park services in a unified manner. Evaluating the rationality of the network structure of the urban park system can provide a basis for optimizing the urban park system. This research adopts the social network theory and relevant methods to, in combination with the supply and demand of urban park services, construct a social network of the urban park system based on human ecology relationship. The research finds that there is an imbalance in the spatial distribution of important network nodes and a mismatch between park level and network hierarchy in the network structure of the current urban park system, and quantitatively evaluates the structure of the urban park system. Based on this, the research proposes the following specific optimization measures. 1) Pay attention to the needs of specific groups and improve service efficiency: Matching types can reflect the adaptation of supply and demand of urban park services at the current stage, and should be upgraded in combination with urban development and optimization objectives to cope with the possible risk of imbalance between supply and demand due to the increasing urban population in the future. 2) Improve the density and service level of parks: High-hierarchy and low-level mismatched parks include community parks in the first-hierarchy network and general parks in the second-hierarchy network. It is supposed to control the scale and development intensity of residential lands around these parks, and improve the quality and resource allocation of such parks in terms of park characteristics, cultural activities, landscape aesthetics and activity facilities. 3) Reasonable positioning function and optimization of park configuration: Low-hierarchy and high-level mismatched parks, such as general parks in the second-hierarchy network, general parks in the third-hierarchy network and community parks, are usually far away from residential groups or have a certain scale of residential land around them. It is supposed to take ecological protection as the main goal, reduce or control the investment in park construction, and reserve the potential to provide recreational services after the subsequent surrounding development intensity is enhanced.