In this paper,taking Flammulina velutipes as the material,the polysaccharide is extracted by microwave-assisted method,and acetylated polysaccharide derivatives are prepared,and then its oxidation resistance test is carried out. A variety of system of free radical scavenging experiment results show that the acetylated Flammulina velutipes polysaccharide with different concentrations have scavenging effects on ·O2-,·OH,DPPH·. Compared with the free radical scavenging capability of the sample of Vc,the clearance rate of polysaccharides on ·O2-is almost the same as that of Vc. The reducing power and the ability to clear ·OH and DPPH· of the acetylated Flammulina velutipes polysaccharides are slightly weaker than Vc. Experimental studies have shown that acetylated flammulina velutipes polysaccharides have strong antioxidant activity,and it can be considering to be used in food and drugs production together with other natural antioxidants.