Preparation method of polyporus polysaccharide

The invention discloses a preparation method of polyporus polysaccharide and provides a method for preparing the polyporus polysaccharide through the combination of a membrane separation technology and a freeze drying technology. The polysaccharide consists of polyporus polysaccharide of which the molecular weight is 400-800. The preparation method comprises the following steps: preparing a polyporus umbellatus water extraction; performing preliminary treatment on the polyporus umbellatus water extraction before membrane filtration; concentrating the polyporus umbellatus water extraction through an ultra-filtration membrane; freeze-drying a concentrated solution to form a polyporus polysaccharide product. Experiment results show that the content of the polyporus polysaccharide which is obtained through the preparation method provided by the invention and has the molecular weight of 400-800 is as higher as 91.12 percent, and the polyporus polysaccharide has higher biological activity. The preparation method has the characteristics of simple operation, few steps, low cost and suitability for industrial production.