Abstract: In this experiment, water stress was given to 13-week and 2-year old seedlings of Chinese Tallowtree and the physiological changes of the seedlings were investigated. The experiment results demonstrated that the activities of superoxide flismutase (SOD) in the stressed seedlings increased rapidly in the early stage of water stress experiment and decreased in the later period while the activities of SOD in the normally-grown seedlings had no obvious change, no change of SOD and peroxidase isozymes were observed during the water tress experiment, malondialdehyde (MDA) content in the stressed seedlings were higher than those in the normally-grown seedlings, and free proline content in the stressed seedlings increased abruptly and the final content was even 4~13.4 times of that in the early stage. These suggest that a protective mechanism exists in Chinese Tallowtree which can eliminate the damages caused by water stress.