6-methyl-5-heptene-2 ketone (MHO) induced apple skin disease incidence and the skin effects of reactive oxygen species metabolism were investigated.Red Star apples of cold storage for 210 d were treated with 0.5,1.0 and 2.0 mL/L exogenous MHO.The content of endogenous MHO was after 10 d under 25 ℃,the malondialdehyde and superoxide anion radical and hydrogen peroxide contents in skin,and polyphenol oxidase,superoxide dismutase,catalase,peroxidaseenzyme activities were measured on a regular basis during the shelf life..Results showed that with the increase of MHO treatment concentration,the contents of malondialdehyde and superoxide anion radical and hydrogen peroxide in apple peel increased;Polyphenol oxidase activity gradually increased,superoxide dismutase,catalase,peroxidaseenzyme activities decreased with the increase of MHO treatment concentration;The endogenous MHO content increased and the incidence of skin disease of fruit also increased with the increase of MHO treatment concentration.So that exogenous MHO may reduce the onset of antioxidant enzyme activities to participate in apple skin disease process.