The objective of this study was to investigate rhubarb extract's inhibiting effects on α-glucosidase activities in the small intestines of rats with Type 1 diabetes mellitus. In group A, the rats were given normal salt. Group B received acarbose, while group C received rhubarb extract for seven days. Fasting blood-glucose was measured from the first to the sixth day . Four fixed rats were selected to measure the level of blood glucose two hours after the meal. On the seventh day, two rats from each group respectively, were selected, half an hour after a meal, an hour after the meal and two hours after a meal to measure their blood glucose, C-peptide and insulin as well as extracting and then determining the alpha glycosidase enzymes in their small intestines. The results from each of the three groups showed no significant differences in terms of insulin and C-peptide; and in the case of daily fasting blood-glucose and the fixed four rats' blood-glucose two hours after meal from the first day to the sixth day, and in the acarbose (group B) and the rhubarb extract (group C), the inhibiting effects on α-glucosidase's activities in the small intestines of Type 1 diabetic rats were superior to those with normal salt. Group A and the former two groups, showed no remarkable differences in these inhibiting effects. In conclusion, rhubarb extract, similar to acarbose, can inhibit α-glucosidase activities in the small intestines of Type 1 diabetic rats. There was little effect on the effect of insulin, C-peptide as well as blood glucose after a meal or in the case of rats with Type 1 diabetes that were hungry.