Phosphate release from the core sediments of fifteen areas in Lake Taihu was simulated at different temperatures，and the phosphorus species in the sediments and seasonal variations of the relative ions，such as A1 (1H ).Fe( II ).Ca( II ) and PO^3-₄ were analyzed. The result shows that the areas affected greatly by terrestrial source are steady internal phosphorus sources in Lake Taihu. In more open areas, the physio-chemical adsorption of deposit colloid makes it weak that temperature have an influence on phosphorus release from sediment so as to produce “internal sink” of phosphorus. At sinking area in the Meiliang Bay, transnormal P demand of the local algae would be one of the most dominating reason of sink formation in addition in spring/summer seasons. There appeared source-sink transition at least once in most of the sediment areas. Chemical thermodynamic analysis reveals that Al-P dissolves more easily than Fe-P and Ca-P on the interface, which perhaps is inherent cause in respect to a marked relationship between Al-P in surface sediment and the phosphate release in Lake Taihu. Although Fe-P is considered to be a potential higher phosphorus release source，the oxidating layer formed on sediment surface and strong adsorbing media in shallow lakes, e. g. inorganic colloid and clay mineral, would be the dominant factors in Fe-P release. The net phosphorus flux, in the whole lake, was estimated about 899. 4±573.6t/a, accounting for about one quarter to half of phosphorus loadings, of which the sinking flux was approximately -91.2±42.4l/a.