Water soluble extract of Rhizoma Polygonati Odorati (RPO) was studied for its hypoglycemic effect in diabetic mice and rats. Results showed that RPO significantly lowered hyperglycemia caused by starch loading in both normal and diabetic mice. Four week's administration with RPO reduced fasting blood glucose, decreased glycosylated hemoglobin (GHb), and improved the glucose tolerance in diabetic mice. In diabetic rats complicated with hyperlipemia, RPO prevented and reduced both hyperglycemia and hypertriglyceridemia. The results support the view that RPO may influence glucose or carbohydrate metabolism of diabetic animals in many ways including inhibiting the activity of alpha-glucosidase in digestive canal, and improving the metabolism of glucose and triglyceride.