AbstractNiangziguan, located in Pingding County, Shanxi, has a large cool spring with rich algae resources. The flora and feature of stream algae in Niangziguan has not been previously reported except for the occurrence of some species. We sampled the algae fifteen times from 1984 to 2000. In the research, 107 species of algae have been found, comprising 7 divisions, 32 families and 49 genera. Chlorophyta was represented by the most species, with 45 species from 13 families and 19 genera. Euglenophyta was ranked as second, with 26 species, in 2 families and 7 genera. Charophyta had the least species, with only 3 species, which belonged to 1 family and 1 genus. The algal flora of Niangziguan was mainly divided into 8 kinds of communities: Cladophora-Bangia community, Cladophora community, Chara-Thorea community, Composopogon-Thorea community, Spirogyra-Zygnema community, Vaucheria community, Batrachospermum community, and Jaoa community. In this article, changes in number of algal species and communities are also reviewed. The results show that the species diversity of algae has been decreasing markedly and many species have become endangered. This was mainly caused by human activities, which damaged the habitats of algae. The research provides some important reference data for exploring and utilizing algal resources in Niangziguan.