Xianyu 420 was used in the experiment to explore the effects of nitrogen on physiological characteristics of maize seedlings under water stress.The result showed that the content of chlorophyll band the activities of root were decreased under water stress.Under water stress,nitrogen element can improve the content of chlorophyll a and root,and the activities of SOD,POD,CAT,Asp were increased under moderate nitrogen,and decreased under excessive nitrogen.Under the nomal water of soil,moderate nitrogen improved nitrate reductase activities,and the amplitude of root was biger than that of leaf.There was no difference significantly in nitrate reductase activities of leaf and root under water stress.