Abstract: After 10 h illumination under the light of 50 μmol·m^-2 ·s^-1，obvious speckles could be formed in the place where the Methyl Viologen was dripped as little blobs on the surface of banana leaves. By determining the activity of two chief antioxidative enzymes，superoxide dismutase(SOD)and catalase(CAT)，a significant reverse linear relationship was found between the diameter of Methyl Viologen speckle and the two enzymes activities, showing the close relationship between the speckle diam eter and the antioxidative capacity in bananas． Exogenous active oxygen species could induce the damage such as peroxidafion of membrane lipid in banana leaves , the damaging degree is closely related with the diam eter of Methyl Viologen speckles，this result indicated that the rapid method to evaluate an tioxidation capacity in bananas was feasible.

Key words: Banana, Methyl Viologen, Antioxidative capacity, Reactive oxygen species