Abstract: The supercritical CO₂ extraction process with the ethanol aqueous solution was used to extract the polysaccharide from Dioscorea opposite Thunb,and the response surface methodology(RSM)was used to optimize the process parameters. On the basis of single-factor experiments,extraction time,pressure,temperature and the ethanol content were selected as four independent variables. An experimental design was carried out involving four variables at three levels. The results showed that the optimum process conditions for extraction of Dioscorea opposite Thunb polysaccharide by supercritical CO₂ fluid were:the extraction temperature of 53 ℃,extraction pressure of 45 MPa,extraction time of 2.5 h,the dosage of ethanol content 68%,the estimated and observed values of maximal yield of polysaccharide was 0.287% and 0.2807%±0.0045%,respectively. The results showed that the extraction yield of polysaccharides from Dioscorea opposite Thunb could be effectively improved by optimizing the extraction process with response surface methodology.