Abstract: In this paper, the physiological responses of the three waterbloom2forming cyanobacteria (Microcystis aeruginosa FACHB469, Anabaena flos-aquae FACHB245 and Oscillatoria planctonica FACHB708) at phosphorus limitation in stationary cultures were studied. The phosphorus uptake rate is hyperbolic correlated to the extracellular nutrient concentration as described by the Michaelis2Menten equation. Kmfor phosphorus of M. aeruginosa, A. flos-aquae and O. planctonica was 81260, 21199 and 41926, respectively, which indicated that the tolerant ability to the phosphorus stress was in the decreasingorder of A. flos-aquae, O. planktonica and M. aeruginosa in the phosphorus deficient condition. The capacity to luxuriously uptake phosphorus of M. aeruginosa was higher than that of O. planctonica and A. flos-aquae. This result was consistent with the phosphorus uptake kinetics experimentsof the three cyanobacteria. Alkaline phosphatase acitivity (APA) of cyanobacteria were inversely correlated with external phosphorus concentration. The APA was obviously promoted under phosphorus deficiency stress. The capacity of excreting AP in the three cyanobacteria was significantly different under the same phosphorus limited conditions (A. flos-aquae > O. planctonica > M. aeruginosa). Extracellular APA of A. flosaquae was 10 and 5 times higher than that of M. aeruginosa and O. planctonica, respectively, when they were cultured in phosphorus deficient condition. The studies compared phosphorus uptake kinetics and capacityof excreting AP in the three cyanobacteria, which would help to understand the population succession of cyanobacteria in the environmental waterbodies.