GLEAMS (Groundwater Leaching Effect of Agricultural Management Systems) is a model developed by scientists of the U.S.Department of Agriculture, and is mainly used to evaluate environmental effects of farming practices.The model was used to simulate the cycling of soil nitrogen in the peri-urban areas of Nanjing.Results showed that during the period fromJuly 2003 to July 2005, nitrogen input reached 3 810 kg hm^-2, of which 3 750 kg hm^-2 came from fertilization and animal waste, the rest 57.0 kg hm^-2 was from rainfall and irrigation.Nitrogen output was composed of leaching 1 100 kg hm^-2, runoff 43.0 kg hm^-2, crop uptake 960 kg hm^-2, volatilization 260 kg hm^-2 and denitrification 913 kg hm^-2, thus forming a surplus of 531 kg hm^-2 left in the soil as residue.On such a basis, nitrogen recovery ratio was calculated to be merely 21.6%～25.2%.The results indicate that the agricultural system has low fertilizer use efficiency, but causes much pollution to the groundwater.The findings serve as a scientific basis for exploration of optimal fertilization recommendations and eco-environmental improvement in the region.