In order to measure the effect of 60Coγ-ray irradiation on membrane lipid peroxidation of fresh walnut, fresh ‘Liaohe 4’ walnuts were exposed under 60Coγ-ray with 0, 0.1, 0.5, 1.0, 5.0kGy, and subsequently packaged in 0.03mm polyethylene bag and stored at the temperature about (0±1)℃. The following main indices, including the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and lipoxygenase（LOX）, the malonaldehyde（MDA）content, fine fruit rate and sensory quality, were determined at regular intervals. The results indicated that the irradiation with 5.0kGy accelerated the process of senescence of fresh walnut. But 0.5kGy irradiation remarkably increased the activity of SOD and CAT, decreased the MDA content, and inhibited the activity of POD and LOX. Thus, the membrane lipid peroxidation process in fresh walnut was slowed down and both fine fruit rate and sensory quality were increased significantly. In conclusion, 0.5kGy irradiation was identified as the best dose for the preservation of fresh walnut in the 90d storage period.