Abstract: For a long time, urban green spaces have been managed with a limited number of cultivated plant species mainly for ornamental purposes and with high-precision maintenance and management. This not only creates a problem of landscape homogeneity, but also weakens the function of urban green spaces in supporting biodiversity. Spontaneous plants exist widely due to their strong vitality, environmental adaptability and sensitivity. They regenerate naturally in response to rapid environmental changes and play an important role in low-maintenance landscaping. In order to explore the species composition and distribution characteristics of spontaneous plants in different habitats in park environment, this study took nine urban park green spaces in Beijing as research samples. The habitats were divided into 11 categories, including artificial grassland, cultivated arbor community, waterfront cultivation community and unplanted land, etc. This study investigated and analyzed the species composition and diversity characteristics of spontaneous plants in these habitats. The results show that: (1) A total of 247 autochthonous plant species were investigated, belonging to 67 families and 179 genera, with native plants being the main species (70.45%); there were six life types, of which annual herbs or biennial herbs were the most abundant, with a total of 99 species, accounting for 40.08% of the species. (2) Among different frequency types, low frequency species appeared most frequently in spring, summer and autumn, accounting for 66.88%, 70.97% and 73.91% of the total species in that season, respectively. (3) Among the 11 habitat categories, cultivated arbor communities and waterfront cultivated communities supported the largest number of spontaneous plants, with 163 and 134 species, respectively; compared to other habitats, the diversity of spontaneous plants was higher in the rockery and unplanted ground habitats. The research results show that strengthening the construction of diverse habitats for spontaneous plants in parks can better protect urban plant diversity.