Abstract: The agricultural nonpoint source pollution has already become one of main environmental pollution problems. Nonpoint source pollution caused by nitrogen from cropland with increasing use of nitrogenous fertilizer became the major factor seriously causing water quality degradation seriously. In this paper, authors have collected recent published research data on nitrogen loss in farming land cited in Chinese academic journal web and some foreign references. The results indicated that there exist four main ways of nitrogen loss on the fertilized farming land, including ammonia volatilization, runoff erosion, soil leaching, nitrification and denitrification. Some factors affecting nitrogen loss intensity and environmental problems caused by nitrogen loss were also discussed. Effects of ecological shelterbelts on the nitrogen loss process and possible factors determining their ecological efficiency were also analyzed. Ecological shelterbelts could control the water body pollution or take off eutrophication caused by agricultural nonpoint source pollution in certain degree, and increase use efficiency of nitrogen in the soil. Some suggestions were given about how to improve shelterbelt structure, allocation and function aiming at alleviating nitrogen loss.