Phosphorus is an essential element for phytoplankton growth and also one of the key factors in eutrophication control. In oligotrophic waters with limited phosphorus, algal species which can effectively utilize the organic phosphorus are likely to dominate in the phytoplankton community structure. To study the effects of organic phosphorus on the succession of the phytoplankton community structure, we collected water samples from three reservoirs:Xipi Reservoir (Bacillariophyta, 70.3%;Pyrrophta, 19.1%; Chlorophyta,9.3%), Shanmei Reservoir (Bacillariophyta, 31.3%;Pyrrophta, 59.2%; Chlorophyta, 3.5%) and Thirty-Six-Feet Lake (Bacillariophyta, 43.1%; Pyrrophta, 50.5%;Chlorophyta, 5.0%). For comparing to an inorganic phosphorus source (NaH₂PO₄·2H₂O), we used the adenosine monophosphate (AMP) as an organic phosphorus source for a 20-day cultivation, and discussed the variation in the growth and the succession of the phytoplankton community structure. The results illustrated different increasing rates of the phytoplankton biomass in Xipi Reservoir (6.5-fold), Shanmei Reservoir (2.1-fold) and Thirty-Six-Feet Lake (1.9-fold). Pyrrophta and Chlorophyta became the dominant phytoplankton groups with AMP as the phosphorus source, and their relative abundances were 81.8% and 16.7% in Xipi Reservoir, 55.2% and 33.5% in Shanmei Reservoir, and 73.2% and 24.3% in Thirty-Six-Feet Lake respectively. In Xipi Reservoir, Peridiniopsis Lemmermann had the highest utilization capacity for AMP, and its relative abundance reached 81.8%. Our work suggested the strong promotion of AMP in the proliferation of Peridiniopsis Lemmermann in Pyrrophta, contributing to the variation in the phytoplankton community structure.