Abstract:This paper，with Xinjiang 'new 2' thin-skinned walnut as material and vaccinated sterile water as control group，explored the change pattern of enzymes related to reactive oxygen metabolism in fresh walnut with different water content after artificial inoculation of A.flavus from natural mildew walnut.The results showed that in the early stage of the infection，fresh walnut with different water content rapidly accumulated reactive oxygen species，and enzymatic clearance system was activated.Thus different antioxidant enzymes significantly increased and reached the peak to resist the pathogenic microorganisms.However，with the growth of infection time，the ability of the enzymatic clearance system decreased，and reactive oxygen species accumulated in a large amount，thereby destroying the cell membrane structure of the fruit as well as speeding up its aging and decay.When A.flavus infected fresh walnuts with 25% water content，the antioxidant enzyme activity of the enzymatic clearance system was significantly higher than that of fresh walnuts with other water content.