It was investigated the algae in the Gongbu Nature Reserve,Tibet.The results showed that 189 species (including varieties) were found.Bacillariophyta has most species,with 109 species of 18 genera in 9 families.Chlorophyta was the subdominant division,with 50 species of 20 genera in 9 families.Cyanophyta was ranked as the third dominant division,with 28 species of 10 genera in 8 families.They were belonging to 5 divisions,28 families,and 50 genera.Bacillariophyta and Chlorophyta dominated in species.Rhodophyta and Chrysophyta had the least species,with just only 1 species,which belonged to 1 family and 1 genus,respectively.There were 7 types of algal community in the Gongbu Nature Reserve,namely Oscillatoria community,Rivularia community,Nostoc community,Hydrurus foetidus community,Cymbella community,Ulothrix community,and Zygnema-Mougeotia-Spirogyna community.Water quality was evaluated by indicator algae analysis.It represented that the overall water quality was good,and the water had not been polluted seriously.Most of the waterbodies were β-mesosaprobic zones,and the others were oligosaprobic zones.The floristic characteristics in the Gongbu Nature Reserve are typical plateau cold water streams with fast flow.The species which represented the source of mountain stream could be observed obviously,and pollution-resistant algae were rarely found.This study could provide suggestion for water and algae diversity protection in this area.