Abstract: ObjectiveDiffusion process parameters in Salvia miltiorrhiza Bunge polysaccharide extraction was opti-mized and antioxidant activity was analyzed, in order to provide reference basis for development and research of S. miltior-rhiza polysaccharide products. MethodWith liquid to material ratio (A), extraction temperature (B) and extraction time (C) as independent variable, extraction rate of S. miltiorrhiza polysaccharide(Y) as response value, extraction process of S. miltiorrhiza polysaccharide was optimized using response surface methodology with three factors and three levels. Mean-while, scavenging effects of S. miltiorrhiza polysaccharide on hydroxyl radical were measured. ResultThe quadratic multinomial regression equation of S. miltiorrhiza polysaccharide extraction was presented as follows: Y=1 . 94-0 . 041A-0.056B+0.022C-0.046AB+0.13AC-0.03BC-0.24A2-0.75B2-0.44C2. The interaction of extraction temperature and extrac-tion time had significant influence on S. miltiorrhiza polysaccharide extraction(P<0.05). The optimal diffusion process con-dition was as follows: liquid to material ratio 25∶1(mL/g), extraction temperature 75 ℃, extraction time 90 min. Under such condition, polysaccharide extraction rate reached 1.94%, which was close to the expected value 1.97%. S. miltior-rhiza polysaccharide had obvious scavenging effects on hydroxyl radical, and the scavenging effects strengthened as mass concentration of polysaccharide increased . The scavenging effects reached maximum ( 42%) when mass concentration of polysaccharide was 4.5 mg/mL. ConclusionThe diffusion process parameters optimized by response surface method-ology are reasonable and reliable, which can be used in extraction process of S. miltiorrhiza polysaccharide. S. miltiorrhiza polysaccharide enjoys certain in vitro antioxidant activity and can be developed as natural antioxidant in food and pharma-ceuticals indusrties.