Abstract: We investigated the effects of exogenous polyamines on growth, photosynthetic characteristics and membrane lipid peroxidation in 2 cultivars of cucumber seedlings with different resistance to hypoxia stress. Photosynthetic rate and water utilization efficiency were increased, but malonic dialdehyde content and membrane permeability were decreased with polyamine treatment under hypoxia stress. At the same time, the fresh weight and dry weight was increased. Under hypoxia stress, the application of exogenous polyamines increased photosynthetic rate in leaves, promoted growth, and alleviated stress damage. In addition, the effect of exogenous polyamine to cultivar Zhongnong No. 8 was more obvious than that to Lübachun No. 4.