The phytoplankton biomass and concentrations of N and P in Lake Dianshan were investigated from January to Decem-ber, 2009, and relationship between phytoplankton distribution and nutritional factors was correlated by Canonical Correspondence Analysis.The results showed that there were two biomass peaks of phytoplankton within a year in Lake Dianshan.The one peak was in spring (March and April), and the other in autumn (August).The biomass of phytoplankton in spring(39.68 mg/m³)was higher than that in autumn (29.86 mg/m³).There were significant relationships between the nutrient concentrations and algae bi-omass in different seasons.The growth of phytoplankton was limited by phosphorus when the bacillariophyta and chlorophyta were dominant in Lake Dianshan from November to January.However, the growth of phytoplankton was limited by ammonium when the cyanophyta and chlorophyta were dominant in the lake from May to August.The higher nitrogen and phosphorus concentrations can-not significantly accelerate the growth of phytoplankton during the two outbreak periods of February-March and September-October, because there were interacted effects between nitrate and phosphorus.