Method for purifying four polysaccharide products from heparin sodium by-products

The invention discloses a method for purifying four polysaccharide products from a heparin sodium by-product. The four polysaccharide products including chondroitin sulfate, dermatan sulfate, heparinoid and sulodexide are respectively obtained by the steps of fractional precipitation, hydrogen peroxide oxidation, ultrafiltration, freeze-drying and the like on the heparin sodium by-product. According to the method, the optimal condition of ethanol precipitation at room temperature is determined, energy consumption caused by low-temperature precipitation and high-temperature precipitation is avoided, and the yield of four polysaccharide products is increased by about 10%; by further optimizing the oxidation process, pigments, proteins and nucleic acid impurities are effectively removed by oxidizing for 3-10 hours at the temperature of 35-40 DEG C, the time is saved by 50% compared with the current oxidation technology of oxidizing for 6-24 hours by hydrogen peroxide at the temperature of 30 DEG C, and the produ