This study was carried to investigate the antidiabetic effect of ethanol extract of Smallanthus sonchifolius(S.S) in Streptozotocin(STZ)- induced diabetic rats. Diabetes was induced by intravenous injection of STZ at a dose of 43mg/kg dissolved in citrate buffer. The ethanol extract of S,S in leaves and root were orally administrated once a day for 7 days at a dose of 1,000mg/kg. The contents of serum glucose, triglyceride(TG), total cholesterol were significantly decreased in S.S treated group compared to the those of STZ-control group. The content of hepatic glycogen and activity of glucokinase(GK) were significantly increased,and activity of glucose-6-phoshatase(G-6-Pase) was significantly decreased in S.S treated group compared to the those of STZ-control group, but activity of glucose-6-phosphate dehydrogenase(G-6-PDH) was not significantly increased, These results indicated that ethanol extract of S.S would have antidiabetic effect in STZ-induced diabetic rats.