Abstract: Phosphorylation modification of chicory (Cichoricum intybus var. foliosum Hegi) polysaccharide was explored by phosphate method. The conditions for the phosphorylation of chicory polysaccharide were optimized by response surface methodology. At the same time, the antioxidant activity for phosphorylated chicory polysaccharide was still explored. The results showed that the optimal conditions for the phosphorylation of chicory polysaccharide was as follows: Molar ratio of polysaccharide to sodium tripolyphosphate was 1:10, temperature was 81 ℃, time was 3.3 h and pH was 7.1. Under these conditions, the content of phosphate in polysaccharides was 4.75%. The results of infrared spectrum analysis confirmed that the modified chicory polysaccharides contained phosphate groups. The results of antioxidant activity test showed that the DPPH radical scavenging rate of phosphorylated chicory polysaccharide increased by 11.28% compared with chicory polysaccharide. In conclusion, the antioxidant activity of chicory polysaccharide could be improved by phophorylation modification.