Abstract: The purpose of this experiment was to research the effect of modified atmosphere packaging on the preservation effect of fresh cut lettuce, lettuce after cleaning, disinfection, dehydration, cutting a series of machining process, with different packaging materials and different proportion of gases to Modified Atmosphere packaging ,refrigerated at 4 ℃, the weight loss rate, VC, chlorophyll, microbial, electrical conductivity, PPO and POD activity of the lettuce were determined every two day, selecting the best material and the best ratio of gas for lettuce. The results showed that the suitable packaging materials and gas ratio of O2 and CO2 were beneficial to extend the shelf life of fresh cut lettuce, under the condition of 4 ℃, using the inflatable proportion of 3%O2 10%CO2 and the packing materials of PE composite nylon for modified atmosphere packaging, was able to maintain the appropriate respiration intensity ,effectively inhibit the growth of microorganisms, decrease the activity of PPO, POD enzyme, and reduce VC, chlorophyll and other nutrient loss. The preservation period of lettuce extended from 4-5 days to 14 days, this has strong application value in the actual production and circulation.