The oxidative stress causes many diseases like cancer, aging, cardiovascular disease, degenerative neurological disorders (Parkinson’s disease, and Alzheimer’s disease) by damage of cell membrane, protein deformation, and damage of DNA due to the oxidation of lipid of cell membrane, protein of tissue or enzyme, carbohydrate, and DNA. It is caused by the reactive oxygen species (ROS) that is produced in the metabolic process of oxygen in cell. The superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in cell systemize the antioxidative enzymes to control the oxidative stress. In this research, it is measured that the survival rate of cell by the typical isoflavonoid of daidzein or genistein, activity of antioxidative enzyme, and ROS level, in order to study the effect of isoflavonoid over the ROS production in cell and antioxidative system. As the similar action of the isoflavonoid with the estrogen is examined, women are encouraged to get bean. In view of this trend, it is very important to find out a combination medicine that lowers the oxidative stress caused by the daidzein in the ovarian cell. In the combined treatment of the typical antioxidant of vitamin C to oxidative stress which induced by daidzein recover the control level particularly lowering the ROS in cell by 30%. However, it made no effect in the combined treatment with genistein. Therefore, the research took the combination effect of daidzein with vitamin C in order to check it effect over the antioxidative system. In conclusion, it was disclosed that the oxidative stress caused by daidzein is related to the lowering activity of SOD, and the specific combination effect of daidzein with vitamin C is related to the recovery of SOD activity.