Abstract: In order to study the community characteristics and their driving factors in the great region of Bosten Lake, four investigations on phytoplankton and physiochemical factors were carried out in 2011. We identified 127 species, 9 species out of which once formed dominant populations. Diatom was predominant in the phytoplankton community all over the year. In winter and spring the phytoplankton community mainly consisted of diatom and dinoflagellate, floating algae being predominant in dys-mesotrophic lakes. However in summer and fall the major composition of phytoplankton were diatom and green alga, eutrophic type being the dominant in the population. The total mean biomass of phytoplankton was (2.512.95) mg/L. The peak of the mean biomass was reached in summer and the lowest in winter. Canoco multivariate analysis indicated that 54.5% of the total variance in the phytoplankton community could be explained with environment variables. The water temperature and the abundance of Cladocera were found to be the most and the second most important factors affecting the distribution of phytoplankton. The phytoplankton abundances were largely affected by the variations of nitrogen contents. Moreover, phytoplankton had profound effects on the concentrations of organism in Bosten Lake.