This experiment was to investigate the antioxidant effect of Sesimtang(SST) on brain tissues of mouse. The experimental groups were divided into three groups and treated ad follows for 15 days ; Normal group(NC), Vt.E admistrated group(PC), SST administrated Group(SST). After the extracting microsome from brain of mouse, those were measured the amounts of oxidant materials like MDA(malonaldehyde) and $H_2O_2$, then activities of antioxidant enzymes like SOD(superoxide dismutase), catalase, NADPH-cytochrome P-450 reductase. The results were as follows; 1. In TBA reaction to measure the amount of MDA, oxidant material of brain tissue of aged rat, both treated groups showed significant decrease. 2. Hydrogen peroxide formation was showed significant decrease in both treated groups than normal group. 3. Superoxide dismutase activity was increased in both treated groups than normal group, and showed little change in SST administrated group than normal group. 4. Catalase activity was increased in both treated groups than normal group. 5. NADPH-cytochrome P-450 reductase activity was increased in both treated groups than normal group.