Abstract: To determine the optimum conditions of the extraction and explore the inhibition of α- glucosidase of glycoprotein from Platycodon grandiflorum with supercritical CO₂ and ultrasonic.Ethyl alcohol was used as entrainer to extract the glycoprotein from Platycodon grandiflorum with supercritical CO₂ and ultrasonic- assisted extraction.Extraction yield and the content of polysaccharide were as detection index to get the optimum conditions.When the extraction temperature was 45 ℃,extraction pressure was 25 MPa,entrainer was 70% ethyl ethanol and extraction time was 1.5 h,the average values of yield and content of the polysaccharide were 27.83% and 62.68%.The median inhibitory concentration on α- glycosidase activity of glycoprotein and Acarbose IC₅₀ were 0.276 mg / m L and0.321 mg / m L. The results showed that supercritical CO₂ combined with ultrasonic extraction of glycoprotein from Platycodon grandiflorum was feasible,simple and pollution- free.Platycodon glycoprotein had stronger inhibitory effect on α- glycosidase。