Abstract: Exposure to hypoxia is stress commonly encountered by plants. To survive prolonged periods of oxygen deficiency, all organisms have had to evolve mechanisms for sensing oxygen shortage and to adjust their cellular metabolism accordingly. In this experiment, the effects of hypoxia stress on anaerobic respiratory enzyme activities and antioxidant enzyme activities in two cucumber cultivars (Cucumis sativus L. cv. Zhongnong No.8 and cv. Lübachun No.4) seedlings with different resistance ability were studied. The results showed that under hypoxia treatment, fresh weight, dry weight and content of protein decreased, while the activities of lactate dehydrogenase (LDH),pyruvate (PDC),alcohol dehydrogenase (ADH),superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT) in roots of two cucumber cultivars seedlings increased significantly, which bear on the resistance of seedlings. The activity of LDH increased significantly in the early period of hypoxia stress treatment, while that of ADH and PDC increase lightly, which reduced the tolerance to hypoxia stress in ’Zhongnong No.8’ seedlings which is hypoxia-sensitive to hypoxia stress cultivar. The activity of LDH increased tardness, the activities of PDC and ADH of ’Lübachun No.4’ increased much more than that of ’Zhongnong No.8’, which could increase the resistance of ’Lübachun No.4’ under hypoxia.