Abstract: In this paper, aiming at the extraction of Usnea polysaccharide, response surface methodology ( RSM) with 3 factors and 3 levels was adopted to study the key parameters in order to increase the yield of Usnea polysaccharide. A second order quadratic equation was established, and the applicability of the model was verified.The results showed that the effect order of three factors on the yields of Usnea polysaccharide were as follows: extraction time, extraction temperature and ratio of sample to water. The optimum conditions of Usnea polysaccharide extraction were: the extraction temperature of 80℃, extraction time of 3.00h, ratio of sample to water of 40∶1. Under the optimization conditions the yield of Usnea polysaccharide reached 80.16mg /g, meanwhile the results indicated that the feasible model fitted well with the experimental data.