Abstract: Effects of supplemental supply of water and N upon maize root physiological characteristics and nutrient uptake were studied under a condition of limited root-grown space. Results showed that under anormal root-grown condition, supply of water and N stimulated root growth, increased total root absorbing area, enhanced actively absorbing area and TTC-reducing amounts, promoted nutrient uptake, and finally led to crop yield increase. Water function to roots grown in a limited space was similar to those grown under a normal condition while N function was controlled by water supply. Supplemental irrigation enhanced N effects, and therefore under an irrigation condition, N supply promoted root growth, improved root physiological characteristics, and decreased the detrimental effects resulting from limitation of the root-grown space. Without supplemental irrigation, N function was greatly affected, and its supply brought about decrease of root biomass and physiological characteristics. In this case, the detrimental effects resulting from limitation of the root-grown space were increased.