Abstract: In the process of high-quality development of mega cities in the new era, cultural service of green space ecosystems is an important content to realize people-centered urban development, and is also one of the concrete manifestations of the coordinated development of human and urban ecological environment. At present, existing researches are largely from a single point of view, lacking quantitative evaluation of functional value from the perspective of citizens, and it is difficult to objectively analyze the current situation and demand of cultural service function of green space ecosystems in mega cities. Taking Shanghai as an example, this study constructs the evaluation index system of cultural service function value of urban green space ecosystems from the perspective of ecosystem cultural service function, which covers human settlements, cultural heritage, education and aesthetics, and comprehensively evaluates the value level of various functions by using the entropy weight method and fuzzy comprehensive evaluation method, and further analyzes and discusses the differences of functional value by using importance-performance analysis and one-way ANOVA. It also puts forward specific policy suggestions on improving the cultural service function of green ecosystems of megalopolis.