Abstract: During 1989-1991 the author made a number of collections,getting 1465samples from 39 counties and cities of Guizhou Province.The identification result shows that there are 5 species and 8 varieties of Pediastrum in Guizhou.Among them,P.Simplex var.quadrilobus Y.X.Xiong is a new variety and P.simplex var.echinulatum Wittr is recorded for the first time in China.According to J.Komarek's system(1983),the 13 taxa are described,and a key to the species and varieties including their distributions in Guizhou is also given in the paper.