Abstract: Corncob pretreated by steam explosion was used as the substrate of xylanase for the preparation of xylose by enzymatic degradation, and the hydrolysis process was optimized by response surface methodologies (RSMs). According to the results of single factor experiment, five parameters which had great influence on the yield of xylose were selected for 53 full factorial experiment designed by Box-Benhnken central composite method. The obtained optimum conditions of enzymatic hydrolysis of corncob pretreated by steam explosion were:xylanase amount 13.05 U/g(based on corncob), water-feed ratio 13.2:1(mL:g), enzymatic time 5 h, temperature 47.3℃, pH value 5.84. Under the optimum conditions, the yield of xylose reached upto 83.24%.