Abstract: Aquatic systems are an important source of nitrous oxide emissions．N₂O concentrations and fluxes from water surface and its concentrations at both the top and the bottom of well water were monitored in Taihu Lake Region．The results show that high N₂O-N concentrations(13．09ug／kg)are dissolved in well water，resulting in high N₂O-N fluxes (90．85ug／m²·h)from well water surface．Analysis of N₂O concentration dissolved at the top and the bottom of water suggests that during the warm season，the well water may be served as a sink for N₂O and there is an obvious difference between the top and the bottom water and between different sampling times．There exists a significant positive relation-ship among dissolved N₂O concentration，N₂O flux，nitrate concentration and water temperature．The well systems are an important so urce of N₂O and denitrification is proceeding actively in the well water．