Abstract: Plants that spontaneously grow in urban areas need less maintenance and perform many ecological functions. Integrating spontaneous plant communities into park planning and design is an important idea to protect urban nature and improve biodiversity in European and American countries in recent years. Using the sampling method, through field investigation of spontaneous plants in 39 parks of various types in Beijing, this research analyzes the characteristics of species composition and community classification of spontaneous plants. The results showed that 1) the 242 spontaneous plant species recorded in this research belonged to 52 families and 166 genera. They contained 10 life forms, represented by 96 species of perennials and 78 species of annuals. 2) The three parks with the largest number of species were Fragrant Hill Park, The Old Summer Palace and Olympic Forest Park. 3) Of all the park types, large urban parks contained more species. 4) In different seasons, spontaneous plants were classified into different community groups, with similar dominant communities in different parks. The research proposes that in future conservation and application of these plants, spaces should be reserved reasonably for the growth and succession of spontaneous plants, stressing the design of spontaneous communities with different characteristics in different parks, and constructing communities according to specific environmental conditions and species habits.