The Dabie Mountains region is rich in plant resources, with complex floristic composition and ancient origin. It is a link connecting the three major flora in East, North, and Central China, and is also an important ecologically functional area for biodiversity protection and water conservation in China. In this study, the representative forest plant communities were selected along different altitudes in Duozhijian, Anjiping and Qilingou areas on the south slope of Dabie Mountains. The biodiversity of forest plant communities on the south slope of Dabie Mountains was comprehensively analyzed from the aspects of species diversity, evenness and richness of different plant community types and levels and their relationship with altitude factors. The results showed that: 1) The southern Dabie Mountains were divided into 20 forest plant community types, with a total of 449 species of plants belonging to 108 families and 270 genera. 2) The species richness index of each level of forest plant community was herb>tree>shrub; The Shannon Wiener index and Simpson index showed trees>shrubs>herbs; The changes in the Pielou index were complex. 3) The species richness of each level of forest plant community decreased with the increase of altitude; The Shannon Wiener index and Simpson index also showed a downward trend with the increasing altitude, but the herb layer showed an upward trend after 1400 m. In the tree layer, the Pielou index decreased with the elevation; in the herb layer, it decreased first and then rose; and in the shrub layer, it increased with the elevation, but its fluctuation was more intense. The large-scale sampling and observation of forest vegetation on the south slope of Dabie Mountains can comprehensively show the overall situation of species distribution, the spatial composition of forest plants, and their relationship with altitude factors. It can provide more comprehensive and real data for the protection of biodiversity on the south slope of Dabie Mountains in the future, so as to provide theoretical basis and practical significance for the protection and sustainable utilization of biodiversity in Dabie Mountains.