Abstract: In order to investigate the effects of different irrigation patterns on root growth and water use efficiency of maize and the differences among genotypes, the field and rain-out shelter experiment with different genotypes of maize (hybrid Hudan 4 and its parents 803 and Tian 4) were carried out. The result showed that hybrid maize Hudan 4 existed marked heterosis in root growth, root profile distribution and water use efficiency. The root length density of hybrid maize Hudan 4 was higher than that of its parents at shallow soil layer under full irrigation condition, but the root length density of Hudan 4 was markedly higher than that of its parents at whole soil profile under water stress conditions. Meanwhile, the root system distribution of same maize genotypes were different under different irrigation patterns. Compared with fully irrigation, no irrigation at jointing stage resulted in the more root distribution at deeper soil layer, which ensured the uptake and use of deeper soil layer water for maize. Root growth produced obvious compensation effect irrigated at later stage (head and filling stage), decline rate of root growth was alleviated at shallow soil layer. Water use efficiency of maize was markedly increased with no irrigation at jointing stage and rewatering at head and filling stage. Therefore, optimizing root profile distribution by rational irrigation is reliable approaches to raise water use efficiency of maize under drought conditions.