Abstract: Eight sample plots were established for investigation on plant species composition and diversity at Rhododendron protistum var. giganteum communities of Gaoligong Mountain, Yunnan province in 2014. The results indicated that the communities could be divided into four layers, namely upper tree layer, lower tree layer, shrub layer and herb layer. There were 30 species belonging to 14 families and 23 genera at tree layer, 25 species belonging to 16 families and 22 genera at shrub layer, 21 species belonging to 14 families and 21 genera at herb layer. The investigated communities had high diversity, evaluated by Shannon-Wiener index, Simpson index and Margalef index, especially the tree layer, was more diversified than shrub and herb layer. Average height and DBH of tree layer had positive relation with Margalef index until a certain value.