To evaluate Biliuhe reservoir pollution condition and provide guidance for the future development, physicochemical factors, abundance, biomass, species composition and biodiversity of phytoplankton were studied in Biliuhe from August 2014 to May 2015， combined with the result of CCA analyses. A total of 310 species, 124 genera 8 phyla were found in the survey area, including 17 genera and 35 species belonging to Cyanophyta, 86 species, and 26 genera belonging to Bacillariophyta, 20species and 9 genera belong to Euglenophyta, 59 genera and 148 species belonging to Chlorophyta, and others belonging to Pyrrophyta, Chrysopphyta, Xanthophyta and Cryptophyta. The taxon of dominant species was very more, but the dominance degree was very low. The dominant species of rivers and periphytic algae was mainly Bacillariophyta. There were seasonal differences in dominant species of reservoir. The phytoplankton had an abundance ranging from 0.28 and 1.23 107ind./L, and the biomass ranged from 1.41 and 5.50 mg/L. The maximum phytoplankton abundance occurred in May, and the next was in August and October, and the minimum occurred in January. Shannon-Wiener and Pielou indexes were better in general, and phytoplankton community structure was more stable. The results of CCA indicated that TP, TN, DO, NO2-N and NH3-N were related with the concentration of Chla, abundance and biomass of phytoplankton. The water of Biliuhe Reservoir was inmoderately eutrophic level. And compared with historical data, it showed that water quality tends to be stable and no obvious changes in recent years.