A very significant linear relationship was found between the capacity of scavenging DPPH free radical and concentrations of six antioxidants (r=0.898～0.994)determined by spectrophotometry.There was an obvious difference in the capacity of scavenging DPPH free radical among different antioxidants. Both scavenging DPPH and inhibiting the oxidation of adrenalin were closely related with the concentration of ascorbic acid. The change of DPPH levels is more sensitive than that of adrenalin in the presence of ascorbate. The antioxidative ability in leaves extracts of two woody plants grown under different light intensities was measured by either scavenging DPPH or inhibiting the oxidation of linoleic acid. The same conclusion was drawn through these two assays. It is suggested that scavenging DPPH free radical is a rapid,simple,sensitive and practical assay for the evaluation of antioxidative capacity in plants.