This work aimed to prolong the preservation time of Brassica campestris L. The effect of five different proportional gas concentrations on physiological and biochemical changes of Brassica campestris L at 4 ℃ were investigated using PE as packaging materials in this paper. The results showed that the treatment with O2 5%, CO2 8%, N2 87% could effectively inhibit the activity of peroxidase (POD ) and polyphenol oxidase (PPO), enhance the conductivity, and decrease respiration rate, weight loss rate, loss of vitamin C and degradation of chlorophyll. The preservation time was extended to 35 days and it had a better preservation effect.