Abstract: The research project team conducted a comprehensive and systematic investigation on the plant vegetation in Dianchi Lake Basin from August 2020 to June 2021. Using the typical sampling method, a total of 31 quadrats were set to investigate the semi-wet evergreen broad-leaved forest in Dianchi Lake Basin, and studied the semi humid evergreen broad-leaved forest in Dianchi Lake Basin from the aspects of community characteristics, species composition and distribution characteristics. The results shows that there are few existing semi-wet evergreen broad-leaved forests in the basin, which are mainly distributed in the north and west of the basin. The community degradation is serious, which is characterized by prominent fragmentation, reduced community height, sprouting clump, the endemic ratio is low, the floristic secondary index is higher, and difficult natural regeneration of community constructive species. According to the results of cluster analysis, the investigated quadrats are obviously divided into five types(formations), which are sorted according to the number of distribution points and area: Cyclobalanopsis glaucoides community, Lithocarpus dealbatus community, Cyclobalanopsis delavayi community, Castanopsis orthacantha community and Castanopsis delavayi community. The Jaccard similarity index among the five formations ranged from 0.1111 to 0.2566, which showed very dissimilarity and medium dissimilarity as a whole, reflecting the obvious boundary between formations. There are 454 species of wild vascular plants in 31 quadrats, belonging to 106 families and 266 genera. The community is rich in species, but the floristic secondary index reached 48.92%. Among them, the herb layer has the most significant response after being disturbed, followed by shrub layer, interlayer layer and tree layer. The results of this study can provide a reference basis for the protection and management of semi-wet evergreen broad-leaved forest in Dianchi Lake Basin.