Exploring the relationship between park green spaces and urban functional spaces provides valuable insights into the production of organically integrated urban spaces that combine production, living, and ecological functions. It also offers guidance for urban spatial structure adjustments and supports the development of park-centered cities. Recent studies have demonstrated that park green spaces offer significant ecological and social benefits; however, evaluations have mostly focused on specific indicators of park green spaces, lacking a detailed and comprehensive assessment. Therefore, this study aims to combine multi-source data and various indicators using methods such as spatial profile analysis and geographical detectors to assess the effectiveness of park green spaces in influencing urban clustering. Firstly, it was determined that both park green spaces and urban single and integrated functional spaces in Hangzhou exhibit clustering distribution. Secondly, by measuring the impact of 12 park green spaces on the clustering of urban functional spaces, specific results were obtained. It was found that there are significant differences in the impact effectiveness across different park green spaces. Thirdly, exploring the factors influencing the agglomeration effect of park green spaces on urban functional spaces reveals that transportation, public services and administration, and residential, commercial, and industrial production functions around parks all influence this effect, albeit with diminishing strength in that order. Interaction between any of these functions further enhances the influence, and the introduction of vitality factors helps eliminate potential misjudgments caused by “ghost city” phenomena. Additionally, park characteristics, such as area, service range, and accessibility, all significantly impact the agglomeration effectiveness of urban functional spaces, with the influence further amplified by the interactions between these characteristics. Finally, directions for future research and planning insights are summarized.