Adopting the combination of pot-cultured plants and locating observation, effect of water and nitrogen regulation on maize root and yield was studied in this test. The results showed that increasing N application rate and normal irrigation was beneficial to improve SPAD value. Except of the jointing stage, the root-shoot ratio of other period was less than 0.3. Under the condition of normal irrigation, increasing nitrogen was beneficial to increase of dry matter weight of root and stem. Water stress and reasonable increase of nitrogen, or normal nitrogen and reasonable water stress, or low levels of nitrogen fertilizer and normal irrigation, could promote the increase of root length, the projection area, root surface area, root volume and average diameter. Under the condition of normal irrigation, appropriate reducing nitrogen was beneficial to the increase of the projection area and root volume, root surface. Suitable increasing of nitrogen application could promote the increase of the average diameter. Suitable increasing of nitrogen could promote root length in earlier stage, and accelerated the disappearance of the root later.Increasing nitrogen application and normal irrigation was beneficial to nitrogen accumulation in root.