Abstract: In order to optimize the conditions of polysaccharide sulfation and improve the antioxidative activity of flue-cured tobacco polysaccharides,the polysaccharides were extracted by ultrasonic-assisted extraction and sulfated by chlorosulfonic acid-pyridine method.The technical conditions of sulfation reaction were optimized with single factor experiment and orthogonal experiments.The antioxidative activity of sulfated polysaccharides was studied by DPPH method and phenanthroline method.The results showed that:1) The optimized technical conditions for sulfation reaction were the volume ratio of chlorosulfonic acid to pyridine 1:6,and reacting at 80℃ for 3 hours.The sulfate group content in sulfated polysaccharides obtained under the above conditions reached 20.03% with the substitution degree of 2.587.2) The antioxidative activity of flue-cured tobacco polysaccharides was significantly improved after sulfation.