Abstract: The preparation of xylooligosaccharide from cottonseed husk was studied in this paper. Orthogonal experimental design was used to select optimal conditions of ultrasonic extraction of xylan. When the ultrasonic temperature was 60 ℃,the ultrasonic time was 30 min,the ratio of material to liquid was 1∶15,the concentration of Na OH was 8%,the extraction rate of xylan was 33.66%. Based on the experimental results of single factor:ratio of material to liquid,the amount of enzyme,the time of enzyme hydrolysis and the temperature of the enzyme hydrolysis,using four factors and three levels of response surface methodology to analyse the influence of each single factor and interaction. The reducing sugar content in response to the value of establishing mathematical model,the optimum conditions were as follows:the ratio of solid to liquid was 1∶20,the accession of the xylanase was 4%,zymohydrolysis time was 3.5 h,zymohydrolysis temperature was 64 ℃. Under this condition,3.35 mg/m L oligosaccharide content was produced.