A Chinese drug formula Tangpingbao is composed of some Chinese herbs and used to treat diabetes. Hypoglycemic aetivity of Tangpingbao wasinvestigated in kunnming mice. Tangpingbao was found to smooth the hyperglycemia caused by starch-loading at both normal and alloxan-induced diabetic mice. But it did not decrease hyperglycemia caused by glucose. We came tothe conclusion that Tangpingbao is an amylase inhibitor decreasing intraluminalamylase activity on starch digestion.