Distylium chinense, the genus Distylium of the Hamamelidacea, is an evergreen perennial shrub between 0.8 and 1.2 m in height, native to the riparian areas and wetlands and a dominant species in the riparian areas of the Three Gorges Reservoir (TGR) region of the Yangtze River and its branches. Our previous studies showed that D. chinense had a certain survival rate in the middle and upper part of the water level fluctuation zone (WLFZ) of the TGR to alternate drought and submergence stresses, but the adaptive mechanisms of its morphology and reactive oxygen species (ROS) metabolism is still unknown. To evaluate its adaptation mechanisms of D. chinense to alternate drought and submergence stresses, a simulation alternate drought and submergence experiment was conducted, and morphology and ROS metabolism of D. chinense seedlings and their recovery growth with different exogenous substances, i.e., abscisic acid(ABA), proline(Pro) and glucose (Glu), were analyzed, including adventitious roots, plant height, base stem diameter, leaf numbers, ROS content, enzymatic and non-enzymatic antioxidant parameters. The results were as follows. (1) The early drought stress stimulated the adaptation of D. chinense seedlings to the later flooding stress.The adaptation mainly refered as more morphological changes of stems and roots i.e., stem base hypertrophy, formation and development of adventitious roots. (2) Comparing to the control group, there were significant increases in the ·OH and the O₂^· in D. chinense seedlings under either drought or flooding stress, which showed oxidative stress responses occurred and their superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) activities and the proline (Pro) contents were also significantly higher than those of controls, which showed that the enzymatic and non-enzymatic antioxidants were induced as a defense mechanism. Under the alternate drought and submergence stresses, the activities of SOD, APX and CAT and Pro contents were higher than those under single drought or flooding stress. (3) Correlation analysis showed that to a certain extent there were coordinated effects between the enzymatic (SOD, CAT, APX) and non-enzymatic (Pro) systems in ROS-scavenging in D. chinense. Exogenous ABA significantly triggered an increase of endogenous Pro contents compared to the controls during the recovery growth and the activity of SOD, CAT and APX was significantly higher than those of the control group under exogenous Pro treatment. Of these, the activities of SOD were significantly higher than those of CAT and APX. The activities of APX increased significantly when soluble sugar (Glu) was added. The ABA, Pro and Glu all had significant influences on the removal of ROS and the ability of D. chinense to up-regulate the SOD activity might be an important attribute for the removal of redundant ROS linked to drought and flooding tolerance. Thus the higher Pro accumulation and effective defense to ROS could be the main physiological adaptation mechanisms for D. chinense under the alternate drought and submergence stresses. The combination of morphological changes and the up-regulating of enzymatic and non-enzymatic anti-oxidative system might be the main mechanisms of D. chinense adapting to alternate drought and flooding stresses. The ABA, Pro and Glu treatment significantly promoted the recovery growth of D. chinense.. The drought in the early stage could improve the tolerance to submergence in the later stage.