This investigation was performed to study the antioxidant activities of Cornus officinalis Sieb extracts and the effect of Cornus officinalis Sieb extracts on glucose, lipid metabolism in diabetic rats. DPPH free radical scavanging activity and superoxide anion radical scavenging of Cornus officinalis Sieb extracts were 94.7% and 92.1%, respectively. Streptozotocin (45 mg/kg body weight, i.p.) induced diabetic rats showed a significant increases of plasma glucose, triglyceride and total cholesterol, concomitantly significant decrease of plasma high density lipoprotein. Glutathione level were decrease in cytosol of liver, lung and brain tissue of rats. Lipid peroxide were increase in microsome of liver cells. Group 1 and 2 were treated with Cornus officinalis Sieb extracts 200 mg/kg body weight and 100 mg/kg body weight for 24 days, individually. Group 1 and 2 rats showed decreased plasma glucose, triglyceride, total cholesterol and lipid peroxide in microsome of liver, and increased plasma high density lipoprotein and glutathione in cytosol of liver, lung and brain. The result suggest that Cornus officinalis Sieb extracts may normalize the Impaired antioxiants status in streptozotocin induced diabetic rats. Cornus officinalis Sieb extracts were used to improve the imbalance between free radicals and antioxidant system due to the diabetes.