Abstract: In order to optimize the extraction method of polysaccharides from purple yam by microwave-assisted extraction. Based on single-factor experiments, extraction time, extraction temperature, solid-solvent ratio and microwave power were selected as influencing factors and the content of polysaccharides as response during extraction. The experiment method was designed according to Box-Behnken central composite experiment, which studied each variable and their interactions effects on the contents of polysaccharide. The quadratic multinomial model on the contents of polysaccharide and each factor was established by using the Design-Expert software. The optimum reactive condition of extracting process was determined by means of response surface method. The results showed that the optimum ultrasonic conditions for polysaccharide were extraction temperature 90℃, extraction time 30min, solid-solvent ratio 1∶30 (g∶mL) microwave power 900W, under which the highest extraction rate of polysaccharides reached with verified value being of 2.852% and the relative error was 0.42% which compared to the predictive value being of 2.84%.