Drought might be the biggest adversity in the nature and might seriously affect maize (Zea Mays L.), one of the most important food-feedstuff crops in China. Although ecologists and physiologists have focused on the response of the activated oxygen metabolism to water stress in maize for a long period and made a great progress, the changes of activated oxygen metabolism, under water stress, and the relationship between the hybrid’s and its parents’ ability to maintain the balance of activated oxygen metabolism in different drought-tolerant maize during the whole life are still lacking. A pot-cultivation experiment, therefore, was conducted in the waterproof shed to try to explore these issues. Different drought-tolerant maize hybrids, Yedan 2, Yedan 13 and their parents were used in the experiment. The result showed that under water stress: (1) The O-〖DD(X-*2〗〖DD)〗2 production rate and the content of H2O2 in maize leaves increased rapidly, whereas the activities of SOD, CAT, ASP, and the content of ASA were increased a little in the early growing stage and decreased obviously in the late growing stage. Consequently the content of MDA, the outcome of lipid peroxidation, was much higher in the whole life period, especially in the late stage. (2) There was a difference in the ability to maintain the balance of activated oxygen metabolism between different drought-tolerant maize hybrids, and much more difference was found in the late period. The high drought-tolerant maize, Yedan 2 and its parents, showed a higher ability to maintain the balance of activated oxygen metabolism. In Yedan 2 and its parents, the increase in the O-〖DD(X-*2〗〖DD)〗2 production rate and the content of H2O2 in maize leaves was less, accompanied by a much more increase in the activities of SOD, CAT and ASP, and in the content of ASA in the early stage, a much more increase in the enzymes’ activity and the content of scavengers in the late stage, and a smaller increase in the content of MDA during the whole life period. The changes were to the contrary in Yedan 13 and its parents whose drought-tolerance was low. (3)The hybrid’s ability to maintain the balance of activated oxygen metabolism was decided genetically by that of its parents. There was a positive correlation in WS/CK ratio between the hybrid and the averages of its parents. Moreover, the correlation was significant in terms of CAT, ASP, and ASA.