The polysaccharides of Schisandra chinensis were extracted by ultrasonic-assisted cellulase enzymolysis from the dried fruit of S. chinensis as raw material， and the extraction process and anti-oxidative stress activity of S. chinensis polysaccharides were studied. Using polysaccharide yield as index， single factor experiment and Box-Behnken response surface test were used to investigate the effects of enzyme concentration， ultrasonic power， extraction time and solid-liquid ratio on polysaccharide yield of S. chinensis， and the ultrasonic-assisted enzymatic extraction process was optimized. A lipopolysaccharide（LPS） induced oxidative stress damage model of HepG2 cells was established， and the levels of malondialdehyde（MDA）， superoxide dismutase（SOD） and reactive oxygen species（ROS） were used as indicators， and the anti-oxidative stress ability of S. chinensis polysaccharides was investigated. The results showed that the optimal extraction conditions as followed： the enzyme concentration was 1 420 U·g-1， the ultrasonic power was 500 W， the extraction time was 46 min， the solid-liquid ratio was 1 g∶32 mL. Under these conditions， the yield of polysaccharides was 22.25%. Moreover， the extracted S. chinensis polysaccharides might improve the SOD level in the LPS-induced HepG2 cells， but reduce the MDA accumulation and ROS fluorescence intensity in the cells， and effectively relieve the LPS-induced oxidative stress in HepG2 cells. The extraction conditions of polysaccharides from S. chinensis were optimized， and it was found that the extracted polysaccharides had good antioxidant stress ability.
