Abstract: Using phytocoenological and phytodemographic methods , we studied the quantitative and qualitative characteristics of plant species diversity of tropical natural forest in Bawangling , Hainan Island. The results showed that 1) plant communities of this area had great differences in the composition of dominant species and there were low species similarities among the communities ; 2) the mountain rain forest in this area had a larger number of species , a higher level of species evenness and relatively weaker dominance of the species than the lowland rain forest ; 3) setting priority according to species rarity , all the plants in this area can be divided into three categories according to their positions and distributions in the communities , namely rare and endangered species , characteristic species , and common species , and 4) some suggestions were put forward for the conservation of plant species diversity in this area.