Abstract: The water quality in the Xueyan town of the Taihu Lake basin was continuously monitored for 12 consecutive months from March 2009 to February 2010 during which two typical rainfall events were encountered.Accordingly, a study on the regularity and characteristic form of nitrogen losses was conducted in the context of different river systems, months, regions, flooding and land-use types.In addition, three studying sites (Shangjian village, Longquan River, Xueyan town) with different spatial scales were selected for analyzing these pollution characteristics during the two rainfall events.The result shows that nitrogen in Xueyan town water is even worse than Category V, and the nitrogen’s most common form is found in the liquid state of nitrate nitrogen.Compared to flooding seasons, the level of nitrogen pollution will be higher over non-flooding seasons.The pollutant load is highly variable and unstable.More specifically, the nitrate nitrogen concentration the townships are lower than that in non-townships.However, the opposite is true for the ammonia nitrogen concentration.Most nitrogen losses are found in ponds, and woodlands (arbor more) had the lowest nitrogen loss.In tea gardens, the nitrate nitrogen has the highest percentage of dissolved nitrogen; while the ammonia nitrogen is the predominant compound in dissolved nitrogen in orchard gardens.Before runoff being generated during a rainfall event, the nitrogen loss is stable.With the increase of runoff, the loss will increase.The increase rate is along different sections of a river.