Both total alkaloids from Feculae Bombycis (TAFB) and natural flavonoids can inhibit alpha-glucosidase activity to depress the glucose level in blood. To investigate the cooperative effect of TAFB and flavonoids on blood glucose, we have studied their combined function compared with individual ingredients on enzymology, in-vitro and in-vivo. In the enzymological assay, the combination of TAFB and flavonoids showed more effective inhibition, compared with either TAFB or flavonoids alone, to alpha-glucosidase activity. In the everted intestine model in-vitro, the combined inhibition of starch hydrolysation and glucose transference to blood was much stronger than with separate components. In short-term studies with normal and experimentally-induced diabetic mice in-vivo, the combination of TAFB and flavonoids also had a stronger suppressive effect on the postprandial elevation in blood glucose after oral administration. In long-term treatment to diabetic mice in-vivo, the compound prescription could depress not only the fasting blood glucose, but also the fasting blood total cholesterol. These results demonstrated that TAFB and flavonoids could inhibit alpha-glucosidase activity cooperatively, which would successfully depress blood glucose level in the therapy of diabetes.