The purple soil is typical in the water-level-fluctuating zone of Three Gorges Reservoir.Nitrogen transformation and soil enzyme activities of the soil were investigated at four water depths (0,2,5 and 15 m) in situ experiment.Results showed that the contents of ammonium and nitrate decreased gradually with the increase of water depth after 180 days flooded.Compared with non-flooded (0 m),the contents of ammonium increased significantly at 2 m depth and nitrate decreased significantly at 15 m depth（P＜0.05）.On the whole,soil ammonium and nitrate were significantly affected by water depth （P＜0.05）.The content of soil inorganic nitrogen (ammonium and nitrate) at 15 m depth was 3.96 mg/kg lower than that of non-flooded soil.Activities of enzymes related with soil nitrogen transformation were significantly influenced by water depth（P＜0.05）.With the increase of water depth,the activities of urease and nitrite reductase showed a decreasing tendency.The activities of hydroxylamine reductase and nitrate reductase decreased first and then increased.Activities of all soil enzymes reached the maximum at 2 m depth.Except for urease,activities of other enzymes were higher than that of non-flooded soil.It is indicated that water depth has an important influence on nitrogen transformation and activities of soil enzymes.