It has been measured that the sediment denitrification rate and the N₂0 natural emission rate at the mouth of Meiliang Bay，Taihu Lake，in the summer of 1997. The measure was performed by Acetylene inhibition technique. The sediment denitrification rate is 1.4-5. 6ptmol/ (m²·h) at the sediment-water interface of Meiliang Bay, Taihu Lake，and the N₂0 natural emission rate is 0. 08-0. 66fxmoI N₂/(m²·h). The exchange trend of NO₃^-between sediment-water interface was discussed as well. It has been pointed out that the sediment denitrification is an important sink in the nitrogen cycling of the Taihu Lake ecosystem. The sediments have a function that absorbs NO₃^-ions from the water column into sediment in the nitrogen exchange process between the sediment-water interface.