Antioxidant effects of Rehmannia vaporata, Discorea Radix, Corni Fructus, Hoolen, Alismatis Radix, and Mountain Cortex Radicis composing Yukmijihwang-tang were studied. The results are as follows; 1. As a result of detecting the defensive effect of each component on cell damage, only the survival rate of cells with 10 ㎎/㎖ Mountain Cortex Radicis was significantly increased. 2. Next, we examined the inhibitory effects of them on ROS occurrence. The result showed significant inhibition of ROS occurrence in cells; with 10 ㎎/㎖ Rehmannia vaporata, cells with 10 ㎎/㎖ Corni Fructus, and cells with 10 ㎎/㎖ Mountain Cortex Radicis. Since the cells with 10 ㎎/㎖ Rehmannia vaporata, however, showed significant cypotoxicity, its result is not meaningful. 3. Finally, the investigation of ROS occurrence / cell found that Corni Fructus and Mountain Cortex Radicis had significant inhibitory effect on ROS occurrence.