Phytoplankton is an important composition of aquatic ecosystem, its community structure and function is always adaptable to water environment and vary with the changes of water environment.The characteristics of phytoplankton community structure could be used as an important index in the assessment of water quality.IIn order to understand the change of water environment in the 22 lakes from the Jianghan Plain, phytoplankton communities and water quality were investigated from April, 2011 to May, 2012. 191 taxa belonging to 7 divisions and 100 genera were identified.Among them, 29 belonged to Cyanophyta, 99 belonged to Chlorophyta, and 40 belonged to Bacillariophyta.The annual mean cell abundance was 0.93×10⁶-84.18×10⁶cells/L, the relative abundance of different divisions indicated that Cyanophyta is the highest(occupied 50.65%), followed by Chlorophyta(29.56%), Bacillariophyta(12.30%), Cryptophyta(6.19%), Euglenophyta(0.56%), Pyrrophyta(0.39%) and Chrysophyta(0.35%).The annual mean of Shannon-Wiener index was 1.44-2.10, with highest value in the flood season.Algal species and the dominant species showed the significant difference in the spatio-temporal distribution.The 22 lakes were divided into 4 groups according to PCA analysis.Characteristics of phytoplankton community and the different conditions, such as the nutrient loading, water quality and the exploitation extent were the reasons for the further polarize in the 22 lakes.It was concluded that the significant spatio-temporal heterogeneous was found in the lakes from the Jianghan Plain, and some lakes faced serious eutrophication due to the over-exploitation.Some lake-specific measurements should be taken for the lake management.