Abstract: The concentration and seasonal dynamics of phosphorus in the sediment(0—5cm,5—10cm)of Lake Donghu were studied at six stations with different nutrient levels. The sampling was taken by a core sampler monthly from March 1998 to February 1999. On the annual average of the six stations,P content in the sediment was 1.15mg/g. The P content in the sediment at Station Ⅰ(Ⅱ)in the present study was 1.42(1.03)times that in the early 1980s. At Station 0 where there was heavy sewerage discharge,the sediment P content was as high as 2.78mg/g,while at the less affected Stations Ⅳ and Ⅴ,it was only 0.52mg/g and 0.50mg/g,respectively. There was a good relationship between the P content of the sediment and the P content of the lake water(r=0.997,n=5,p0.02). By comparing the P content of the sediment and water column,and external P loading in some Chinese lakes,it appears that if the P content of the water column is high and external P loading is large,the P content in the sediment is generally also high. Predictably,the great P pool in the sediment will still be a threat to the water quality of the lake ecosystem even if the external loading is under control.