To investigate the extraction technique of soluble soybean polysaccharide by ultrasonic assistance, four relative factors, including water extraction temperature, ultrasonic treatment time, ultrasonic power and solid to liquid ratio, were optimized through orthogonal test L9 (34 ) on the basis of single factor experiment. The factors influencing the extraction rate of soluble soybean polysaccharide, in the sequence of significance, were ultrasonic treatment time, water extraction time, water extraction temperature and sold to liquid ratio. The optimum extraction technological parameter of soluble soybean polysaccharide was: ultrasonic wave period 20 min, water extraction temperature 90 °C, sold to liquid ratio 1:40, water extraction period 4 h, and the extracting rate was 3.5421% of bean dregs. The method of phenol-sulphate acid was applied to determine the content of polysaccharide. The content of polysaccharide was 96.58％ of extracted soybean polysaccharide sample.