A well-organised park green space (PGS) spatial structure would provide multiple socio-ecological benefits, while promoting the optimisation of urban spaces. However, current research lacks a conceptual definition, effective analytical methods, and dynamic assessments of it. This study constructs a multidimensional framework for the PGS spatial structure, both internally (different types of PGS) and externally (PGS with other different types of urban functional space [UFS]). Taking Nanjing, China, as an example, the PGS spatial structure and its competitive relationship are quantified using the stand spatial structure parameter (SSSP) and Hegyi competition index. We quantify the spatial structure-including the average value of the SSSP (uniform angle index [W], dominance index [U], and mingling index [M]), the stand spatial structure comprehensive evaluation index (FSS), and the proportion of each class. Competitive relationships include competitive intensity and patterns. The findings demonstrate that: (1) The layout differentiation degree of the internal and external PGS has increased
the area difference and type mixing degree has decreased
and the external spatial structure is superior to the internal structure-although less stable, overall. (2) External space dominates PGS competitive relationships, with reduced competitive intensity influenced by residential, commercial service, and traffic spaces. Internal space is primarily influenced by city gardens, which intensifies internal competition. (3) The FSS effectively regulates the PGS spatial structure by integrating W, U, and M, thereby reducing competitive intensity internally and externally. These findings broaden the analytical perspective of PGS, offering a scientific foundation for the efficient allocation of urban spaces.