A technique to produce high-content fructo-oligosaccharides by the mixed- enzyme system of fructosyltransferase and glucose oxidase was investigated. The mixed-enzyme reaction was carried out in a stirred tank reactor containing 40 %(w/v) sucrose with 10 unit of fructosyltransferase and 10 unit of glucose oxidase per gram sucrose for 25 h, at 40 °C and pH 5.5. Highly concentrated fructo-oligosaccharides up to 90 % was obtained by the mixed-enzyme system.