In order to clarify the effect of afforestation of Dodonaea viscosa on the native plant species diversity in karst area of Beipan River, we are adopting the community sample survey method to investigate the plant communities under different D. viscosa coverages (0, 20%, 40%, 60%, 80% and 100%), comparing and analyzing the species diversity of the plant communities. The results are as follows: (1) with the increase of D. viscosa coverage, the number of species in the community and phanerophytes slightly decrease, and the remaining species are mostly herbage of hemicryptophyte, cryptophyte and therophyte. (2) With the increase of D. viscosa coverage, Margalef index, Simpson index, Shannonwiener index and Pielou index all showed a downward trend, the plant species and quantity decrease, the community structure tend to be simple and the stability decrease. (3) With the increase of D. viscosa coverage, the species composition of the community is constantly replaced, and the species substitution rate of herbaceous plants is higher than that of woody plants. However, the variation trend of substitution rate among community species first decreased and then increased, while the species similarity coefficient between adjacent two coverings (0% and 20%, 20% and 40%, 40% and 60%, 60% and 80%, and 80% and 100%) first increased and then decreased. The results showed that when the D. viscosa coverage reaches 60% or higher, the local plant species richness and diversity are relatively low, the species distribution is uneven, the community structure become simple and the stability is poor, which is not good for the community to develop to a higher stage.