Abstract: The biomass, leaf SP content, MDA content, SOD activity, and POD activity of plants at different stages were measured to analyze their physiological responses to flooding stress and exogenous 6-BA by simulating flooding with exogenous 6-BA treatment in pots using annual Salix matsudana × alba cuttings as the material. The findings indicated that the SP content of leaves under flooding stress showed a decreasing trend and reduced photosynthetic product accumulation, the antioxidant enzyme activity increased and then decreased, and the MDA content increased significantly at 45 d. Exogenous 6-BA had a significant effect on photosynthetic product accumulation and protective enzyme system of plants under stress. The study showed that the annual Salix hybrid showed strong tolerance to flooding, and the spraying of 6-BA at a concentration of 30 mg/L in the first and middle stages had a significant effect on improving photosynthetic product accumulation and enhancing the leaf protective enzyme system.