Abstract:A field experiment was carried out to study effects of nitrogen application on grain yield winter wheat (Xinong 9814) and soil NO-3-N. The results show that the yield components such as grain weight per spike, grains per spike and 1000 grain weight are all increased under the moderate nitrogen application, and the highest yield occurs at N 276 kg/ha of nitrogen application, which is about 124.6% of the yield of the control. Among the yield components, spike number has the strongest correlation with yield, and second is kernel weight. Soil NO-3-N mainly exists in 0-40 cm depth, and the soil NO-3-N contents are increased with the increases of nitrogen application. With the wheat grows, soil NO-3-N contents are decreased, especially in the 0-40 cm depth, while, those are almost the same in different depths at the mature period of wheat. Soil NO-3-N accumulations are not changed when nitrogen application rates are between N 0-207 kg/ha, while, the accumulations are rapidly increased when the application rates are larger than N 207 kg/ha. These results indicate that there are NO-3-N redundancy and possible N leaching under high N application.