The quality of starch digestion related to the rate and extent of glucose release is associated with high glycemia-related health issues such as diabetes and other metabolic syndromes. In humans, two types of digestive enzymes, α-amylase and mucosal α-glucosidase, are involved in breaking down starch molecules to absorbable glucose. To evaluate starch digestion in vitro, which is an affordable and efficient way to examine the nutritional quality of starchy foods during the process of product development, it is common to use a combination of porcine α-amylase and fungal glucoamylase to determine the digestibility. Fungal glucoamylase converts α-amylase hydrolyzates to glucose and directly hydrolyzes starch molecules to glucose. Although its functions look similar to human small intestinal α-glucosidase, its hydrolytic mechanism and influence in physiologic responses are quite different. In this article, we review the structure and properties of the small intestine α-glucosidases, including their protein structure, hydrolytic activity, digestion capability, distribution in the small intestine, and the dietary influence in their activity and synthesis.