Reactive oxygen species(ROS) or free radical-mediated oxidative stress plays an important role in the pathophysiologic process of disease state. This study investigated antioxidative effects of Phellinus linteus extract on the generation of 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical, superoxide anion radical(${O_2}^-$), hydroxyl radical(${cdot}OH$), nitric oxide(NO), and peroxynitrite($ONOO^-$) radical and free radical-mediated protein oxidation under in vitro assay systems. This results showed that Phellinus linteus extract effectively inhibited the generation of free radicals in the all assay system with dose-dependent manner and also significantly reduced the protein oxidative level. Thus, the present study indicates that Phellinus linteus extract possesses a potent antioxidant activity and plays a beneficial role against free radical-induced oxidative injury.