Benthic aquatic insects were sampled by qualitative collection method at 3 sites in the streams of Mt.Nankun,Guangdong Province in September,1994.Total 955 individuals which belong to 104 species of 67 genera in 41 families under 8 ordels of aquatic insects were collected. They can be identified by 30 species of 17 genera in 12 families of Trichoptera,30 species of 18 genera in 9 fmilies of Ephemeroptera;12 species of 8 genera in 2 families of Plecoptea;14 species of 12 genera in 8 families of Odonata,9 species of 4 genera in 4 families of Diptera;4 species of 4 genera in 3 families of Coleoptera;2 species of 2 generain 2 families of Hemiptera;3 species of 2 genera in one familv of Megaloptera. Using Shannon-Weiner diversity index,EPT taxa richness,Biotic index and Family-level biotic index to evaluate water quality of 3 sites in the streams of Mt.Nakun.The resuit shown that the 3 sites had dean water quality.