Species diversity of the natural forest communities in Nanling National Nature Reserve,Guangdong, was studied by computing the species diversity indices, species evenness and ecologcal dominance of 9 formations .The species diversity indices (Shannon-Wiener Index)ranged from 2.90 to 5.34 ,species evenness from 0.56 to 0.87 and ecological dominance from 0.05 to 0.25. The differences of species diversity indices became larger with forest types from montane coniferous forests to montane coniferous and broadleaved mixed forests, to hilly and low mountainous evergreen broadleaved forests. The relationships between species diversity,habitat and community stability were also analysed in this paper.