Phosphate sorption isotherms were determined for representative upland and paddy soils in Taihu Lake watershed.P desorped from the soils were also studied by successive extractions with iron oxide-impregnated paper st rips.Although the averaged P sorption maxima of upland soils derived from Langmuir sorption plot was a lit tle higher than thatof paddy soils the po tential of P loss from upland soils to waterbodies was greater because upland soils usually had a much higher P level.The Deg ree of Phosphorus Saturation (DPS), an integrated expression of soil P level and soil sorption capacity, can give good estimate of the amountof P desorped from soils so it can be used as a reliable index to assess the potential of soil P loss via leaching or surface runoff.