Abstract: Separation and purification of glycoprotein which were extracted by super critical CO₂ from Platycodon grandiflorum.Then the monosaccharide and amino acids composition and the inhibition of ·OH of glycoprotein were investigated. The glycoprotein were extracted from Platycodon grandiflorum and purified by DEAE- 52 cellulose column and Sephadex G-75 gel column.Monosaccharide and amino acids of glycoprotein were analyzed by pre- column derivatization with PMP and OPA- FMOC respectively. The results showed that Platycodon grandiflorum glycoprotein was composed of 7 kinds of monosaccharide( average content of 61.82%) and 15 kinds of amino acids( average content of 33.11%). IC₅₀ value of inhibition ·OH was 0.99 mg / m L. The study showed that·OH could be inhibited by the Platycodon grandiflorum glycoprotein effectively,which provided the theoretical basis for the further study on functional food and the drugs manufacture.