Abstract: The effects of soil moisture and nitrogen fertilizer on root growth(root length,weight and root/shoot ratio) of corn are studied with simulated field plot experiment.Results indicate that the application of nitrogen fertilizer makes total root length,surface(0～20cm) root length,root weight increase and root/shoot ratio decrease at the stage of shooting and flowering under both soil moistures.Although nitrogen fertilizer could increase total and surface root length under both soil moistures at the stage of grain-filling,but it decreases root weight and root/shoot ratio under watered soil,while it has no effect on root weight and root/shoot ratio under dry soil.Root/shoot ratio is closely related with N uptake and distribution.