Phytoplankton is very important to keep the balance of aquatic ecosystems as one of primary producers. In the present study, phytoplankton in 13 lakes of Yunnan-Guizhou Plateau were investigated during the summer June-August of 2008, and phytoplankton abundance, biomass, community stnicture and biodiversity were analyzed. A total of 109 taxa (52 green algae, 23 cyanobacteria, 20 diatoms, 14 others) were found in the lakes. Shannon-Wiener indexes of phytoplankton in the 13 lakes were ranged fiom 0.5 to 2.2, which were not significant correlalions with any single factor. Furthermore, phytoplankton abundance and biomass were obviously correlated with TN, TP, COD_Mn and NO₃-N, and species richness was remaritably correlated with TP (< 0.1 mg/L), TN and COD_Mn. In addition, there was significantly negative correlation between Soreswi similarity of ccHumunity structure and variation of trophic states in the 13 lakes. Our results indicated that trophic states of lake can influence phytoplankton abundance, biomass, species richness and Soreson similarity of community stucture.