The aubstance exchange across the water-sediment interface in the north Taihu Lake was studied under the condition of 25℃.The results show that the release levels of nitrogen.phos-phorus and COD in Wuli Lake area are distinctly higher than those in Meiliang Bay, and the aver.age release rates of their NH₄⁺-N, DTP and DCOD are 158.2.2.05, and 27.8mg/(m²·d).Re-spectively.In the northern part of Meiliang Bay, formal nitrogen negatively releases and howev-er, DTP and DCOD release rates are separatively 0.584 and 8.9mg/(m²·d) Morever, the ex-changable amount of the form al nitrogen, phosphorus and DCOD on the water-sedim ent interface has obviously to do with content of the total nitrogen, total phosphorus and organic matter in the corresponding sediments.On the basis of internal pollution source analysis, restraining the release of nitrogen, phos phorus and COD in the part lake area is considered to be one of the important measures to control the water pollution and eutrophication of Taihu Lake.