Abstract: Aphanizomenon flos-aquae (A1 flos-aquae) isolated from eutrophic Lake Dianchi was cultured in BG11 medium, and it was maintained at (25 ±1) ℃ (with an illumination of 20μE/m2.s, under a light/dark cycle of 16 :8) . The growth cycle of A1 flos-aquae was approximately 28d and the growth curve was fit well with the typical“S”model . Concentrations of NO3--Nand PO43--P may affect the growth of A1 flos-aquae with better growth under higher concentration of N and P , but excessive N and P may restrain the growth of A1 flos2aquae. Fv/Fmof A1 flos-aquae can only affected by the absence or unusually low contents of N and P. Nitrate reductase,acid phosphatase under low concentrations of N and P were significantly higher than that of the control (cultured in BG11 medium, p < 0105) . Activities of nitrate reductase and acid/alkaline phosphatase were not linear with the changes of N and P concentration. These results indicated that A1 flos-aquae could adapt to variant circumstances with different nutritional levels due to their physiological and biochemical strategies1.