Abstract: The National Park System (NPS) in the United States leads the development of protected areas in the world, and also formed a relatively complete national park science. This paper selects 10954 scientific papers related to NPS in the past 150 years, and combined with TF-IDF and LDA text analysis algorithms, obtained the composition and evolution trend of national parks science. The results show that: ①The composition of NPS science has formed the overall framework of "four beams and eight pillars". "Four beams" refer to the four interest objects, which are plants, animals, natural environment and human behavior, and "eight pillars" refer to the eight research fields, including public administration, recreation, geology, etc.②The evolution of research popularity of 18 representative words shows that park science has obvious stratification, and has the characteristics of overall rise and different processes. The high-heat area is eternal topics such as land, the medium-heat area is basic research such as biology and emerging fields such as climate change, and the low-heat area is mostly occasional research such as fire.③ Park science is closely related to the development process of the NPS: the initial stage of the NPS focuses on the natural resources survey and the driving factors for NPS establishment; the system improvement stage focuses on the institutional and infrastructure of NPS; the current affairs-oriented stage focuses on major events such as the Great Depression and World War II.; The multidisciplinary integration period presents development of different disciplines based on ecology. Understanding NPS science has very important significance for the development and science of China′s national park system.