Sihosamultang(SST) has been used for the treatment of puerperal fever, liver disease in traditional medicine. The present study was carried out to evaluate the antioxidant effects of SST extract in vitro. The inhibitory effect of SST extract on lipid peroxidant was examined in the linoleic acid autoxidation system. In this test, SST extract significantly inhibited the time course of the lipid peroxidation. And SST extract showed about 73% scavenging effect on DPPH radical. And this extract inhibited not only the lipid peroxide formation induced by hydroxyl radical derived from $ H_{2}O_{2}-Fe^{2+}$ in the rat liver homogenate, but also the superoxide generation from xanthine-xanthine oxidase system in a dose-dependent manner. In addition, SST extract protected the hepatic cell death induced by tert-butyl hydroperoxide. These data indicated that SST might play a protective role against oxidative injury by free radicals.