Diabetes mellitus (DM) is one of the highest morbidity and mortality diseases and is a state of increased oxidative stress. This study was carried out to evaluate anti-oxidant activities of Hovenia dulcis Thunberg in streptozotocin (STZ)-induced diabetic rats. Eighty Sprague-Dawley rats, 6 week-old, were divided into 3 groups at 12hours after STZ induction; Diabetic control group (DW per os DC group), Glibencliamide group (5 mg/kg glibenclimide per os, GLI group) and Hovenia dulcis group (100 mg/kg Hovenia dulcis Thunberg water extract per os HDT group). Normal control group (NC group) was just injected with DW instead of STZ. On day 5, superoxide dismutase (SOD) and catalase activities of HDT group were significantly (P < 0.05) increased compared with DC group and glutathione peroxidase activities of HDT group was more increased than DC group but there was no significant difference.