Abstract: Derivatization technology of polysaccharide from Auricularia auricular was optimized by using Response Surface Methodology, and examining the effect of anticoagulant in vitro after polysaccharide transforming as well. The results showed that selecting p-hydroxybenzoic acid as acyl donor, the best process condition of derivatization of conversion temperature of 55℃, the ratio of polysaccharide to acyl donor of 10∶1, polysaccharide concentration of 0.50mg/mL, that was the most effective condition. The optimal conversion rate was 27.26%under this condition. Conversion polysaccharide could improve the effect of anticoagulant in vitro.