Abstract:Based on data from 50 quadrates, species diversity of plant communities in Baihua mountains were discussed, and measurements of species diversity of quadrates along DCA axis 1 gradient and altitudinal gradient was also carried out. The results showed that: Richness index varied as follows: in forest communities it showed herb layer > shrub layer > tree layer, in shrub communities showed herb layer > shrub layer and Vitex negundo var. heterophylla community showed shrub layer > herb layer. Shannon-Wiener index of the most forest communities showed herb layer > shrub layer > tree layer but Populus davidiana+Larix principis-rupprechtii community showed shrub layer > herb layer > tree layer, and that of shrub communities showed herb layer > shrub layer but Vitex negundo var. heterophylla community showed shrub layer > herb layer. Evenness index of shrub communities showed shrub layer> herb layer, in forest communities it showed tree layer > shrub layer> herb layer Quercus liaotungensis and Populus davidiana+Larix principis-rupprechtii community showed shrub layer > tree layer > herb layer. The specie diversity of quadrates along both DCA axis 1 and altitudinal gradient significantly peaked at the intermediate elevations, but there were some differences: the fitted curves of both richness and evenness with altitudinal gradient were more significant than that fitted with DCA axis 1, while that of diversity showed the opposite trend.