To investigate the effects of high oxygen modified atmosphere packaging on the respiratory intensity and enzymatic activities of fresh-cut lettuce during storage,the lettuce slices were packaged in boxes with 60%O2﹢20%CO2﹢20%N2 and 100%O2 at 4℃ for 14 days,in contrast to that of air treatment.The results showed that the respiratory intensity and enzymatic activities of fresh-cut lettuce were affected markedly by high oxygen modified atmosphere packaging.In packaging with 60%O2﹢20%CO2﹢20%N2 and 100%O2,the respiration was inhibited,and the slower the respiration,the higher O2 concentration;SOD activities were improved and the increases in superoxide radical production were inhibited;the polyphenol oxidase and phenylalanine ammonium-lyase activities were inhibited.