Abstract: In order to study the soil nitrogen migration under different application rates of chemical nitrogenous fertilizer in deep vadose zone, during the course of summer maize growing, 3 chemical N fertilizer levels (142.5, 285 and 427.5 kg/hm2) were set up, the NO3--N, NH4+-N and total nitrogen migration and accumulation in the first 500 cm depth of soil for each treatment were studied. The results showed that impacts of chemical N application rates on NO3--N, NH4+-N and total nitrogen were dramatic, the leaching and accumulation of soil NO3--N, NH4+-N and total nitrogen increased with increasing chemical N application rate, but decreased with the growth of summer maize. Soil NO3--N and total nitrogen accumulation increased with the increase of chemical N application rate in 0-200 cm soil, while the soil NH4+-N accumulation were found to be in the following descending order: the 285 kg/hm2 N application rate> the 142.5 kg/hm2 N application rate> the 427.5 kg/hm2 N application rate, but the difference was no more than 0.1 kg/hm2. After harvest the soil nitrogen accumulation decreased. The influences of different N application rates on soil NO3--N, NH4+-N and total nitrogen changes were mainly in 0-145 cm depth. The soil nitrogen was inclined to accumulate in powder sandy loam and leach into water in sandy loam. The 142.5 kg/hm2 N application rate can effectively reduce the NO3--N leaching, and reduce NH4+-N and total nitrogen content in soil, thus make the risk of groundwater pollution minimum. The groundwater in Beijing is deep, which is not polluted easily by NO3--N leaching. However, large quantity of chemical N application in long-term and the presence of soil macropores can accelerate the leaching and migration of NO3--N in the soils, thus posing a threat to groundwater quality in the Beijing area.