Urbanization has brought about a substantial increase in population growth, and a considerable amount of park green space has been exposed to urban construction land, which has greatly affected the natural and social value of the urban natural capital. Although this problem is serious in developing countries such as China, few studies have been conducted on the basis of a comprehensive evaluation of urban natural areas. This study evaluates the ecological services value of urban wetland parks from two perspectives: 1) the urban economic development brought by urbanization has an obvious artificial influence on an urban park’s economic value and 2) the wetland ecosystem plays an important role in regulating and improving the surrounding urban environment. A flexible evaluation step model and a series of quantitative evaluation methods was constructed and used in a case study of Aha Lake National Wetland Park in Guiyang, China, based on a comprehensive analysis of the social, economic, and ecological values of the park. The results show that the total ecosystem service value of Aha Lake National Wetland Park is 1.92×10⁹ yuan. This article has two main purposes: 1) serving as an innovative quantitative evaluation method of key indicators and 2) establishing a framework of ecosystem services value evaluation for urban parks based on the cascade model.