Taking Songtang reservoir, man-made Pond, Jiazhu River and Water wells as the research objects, ammonia-nitrogen(NH+4-N), nitrite-nitrogen(NO-2-N), nitrate-nitrogen(NO-3-N) and total nitrogen (TN) were studied. Based on dynamic monitoring data of water quality from January to May 2010, nitrogen pollution of water environment of agricultural ecosystems in Qianyanzhou is mainly nitrate-nitrogen(NO-3-N), there was obvious difference between its upper reaches and lower reaches of the groundwater flow field; the maximum and minimum concentration of NO-3-N in Ganjia water well in lower reaches of the groundwater flow field amounted to 22.56and 14.80mg/L, exceeding the standards for drinking water made by the world health organization (WHO), and detection rates were 100%, nitrate radica1groundwater has been found; The content of nitrite nitrogen in man-made pond and Jiazhu River was high significantly to 0.20mg/L during busy seasons, which is extremely harmful to the growth of aquatic life; the concentration of ammonia-nitrogen had no significant difference between river, reservoir and well water, while there was obvious difference along the change of time. The research on the transformation of “three nitrogen” in groundwater can provide the basis for agricultural production and groundwater pollution control.