Abstract: Geochemistry of phosphorus in sediments cores of the Taihu Lake which is a large shallow lake in China is studied by sequential extraction method.There is an abrupt change of both the chemical fraction characteristic of phosphorus and the other physicochemical properties of sediment,such asp H,Eh,LOI and water content at the depth 5 cm to 15 cm in the sediment cores.No significant correlation between the concentration of phosphorus in interstitial water and the bio-available phosphorus in the sediment.Hydrodynamics and aquatic vegetation may be the major factors controlling the geochemistry of phosphorus in the large shallow lake.