Variations of nitrogen (N) concentration and the ratio of N to phosphorus (P) in Lake Taihu may impact P accumulation and allocation of algal cells, and even influence total P concentration in water. In this study, common cyanobacteria (colonial and unicellular Microcystis strains) and a green alga (Scenedesmus obliquus) were cultured in different N ∶P groups (N ∶P=2 and N ∶P=20). Changes in their P forms, content, and distribution (intracellular P (INT-P) and extracellular P (EPS-P)) were explored. Results showed that the total cellular P contents (CTP, including INT-P and EPS-P) of S. obliquus and colonial Microcystis in the low N ∶P group were 2.7 and 1.4 times higher than those in the high N ∶P group, respectively. In the low N ∶P group, EPS-P occupied about 80% of the CTP. Particularly, EPS-P contents of the low-N ∶P treated S. obliquus and colonial Microcystis increased by 3.1 and 0.48 times higher than those of the high N ∶P group. In the low N ∶P groups, EPS content of S. obliquus and colonial Microcystis increased by 51.7% and 63.5%, respectively. However, changes of INT-P were not significant in both species. Moreover, CTP and EPS-P mainly existed as NH₄Cl-P, while INT-P was mainly found as Fe/Al-P. These findings revealed that low N ∶P ratio affects the P accumulation and distribution patterns of algal cells, by promoting EPS secretion and EPS-P accumulation. It may be a potential reason for total P fluctuation in the water of Lake Taihu.