Abstract: In this paper, the urban forest within the built-up area of the main urban area of Nanchong city was sampled according to the green space types, the diversity of vegetation species and tree specifications were studied. According to the current situation of urban forest structure in the main urban areas of Nanchong city, the existing problems were analyzed, which could provide reference basis for the planning of forest cities and the construction of urban forests. A total of 84 families, 164 genera, and 252 species of woody plants were recorded through the survey of 274 standard plots in each type of green space. In terms of frequency of arbor, the top five tree species in the main urban area use were Osmanthus sp. (13.19%) and Ficus virens Aiton (10.55%)、Ginkgo biloba L. (10.55%)、Cinnamomum japonicum Sieb. (9.50%)、Cinnamomum camphora (L.) Presl. (8.18%).The average DBH of the tree was 22.88cm, and the average crown width was 5.90m. Among the types of green spaces in the main urban area of Nanchong, the species composition, diversity and tree specifications of the protective green spaces were lower than that of other green spaces. In the future urban forest construction, the construction of protective green space should be strengthened, and the local tree species with dust retention, sterilization and other functions were preferred. Corresponding shrubs and herbs and other plants should be matched, which could enrich plant configuration models and improve the safety and stability of urban forests.