The research extracted polysaccharide from the Chinese yam by the methods of enzymolysis. UV scanning and infrared spectroscopy were used to identify the components and structure. Using PNPG as the substrate, the enzyme-inhibitor model was used to study the inhibition ability of polysaccharide from the Chinese yam of the α-glucosidase, and the double reciprocal plot method was used to determine the type of inhibition. The UV scanning results showed that the extract does not contain nucleic acids and proteins, and the infrared spectra showed that the extracts had the characteristic absorption peak of polysaccharide. The enzyme-inhibitor model showed that the polysaccharide from the Chinese yam had stronger inhibition effect on the activity of α-glucosidase. The inhibition type was competitive inhibition, with inhibition constant factor K_i of 65.78 mg/mL.