Phosphorous is one of the key elements that lead to eut rophication.Pseudomonas sp.(X strain)was isolated from Microcystis aeruginosu in Taihu Lake.A group of test was designed to study the growth and phosphates [K₂HPO₄+KH₂PO₄(1:1)], organic phosphates (ATP), phosphorus fraction and growth factor.The results showed that the growth of X strain was not affected by inorganic phosphates and rest rained by ATP.The strain prefered inorganic phosphorus too rganic one when both available.X strain made use of particular phosphorus and extracted of algae that substituted for yeast extracts as growth factor.