Abstract: Alkali liquor pretreatment conditions for lignocellulosic corn cob were optimized to remove lignin and improve the enzymatic hydrolysis yield of hemicellulose and cellulose. By multilevel of single-factor test and orthogonal test methods, the results for the optimal pretreatment conditions were as follows : reaction time 12 h, temperature 70℃, liquid to solid ratio 23:1, aqueous ammonia concentration 2.5%(W/V), hydrogen peroxide 0.6%, sodium silicate 5%, magnesium sulfate 0.05% in reaction mixture. Under this optimal condition, the residue yield of corn cob was 59.74%, the remaining rates of hemicellulose, cellulose, and lignin were 56.60%, 86.20%, 11.83%, respectively, in corn cob. The enzymatic hydrolysis yield of hemicellulose, cellulose, total of corn cob residue was 41.36%, 88.09%, 69.21%, respectively, by two steps hydrolysis (xylanase and cellulose). Compared with the untreated straw, the enzymatic hydrolysis yield increased 39.18%, 40.89%, 44.88%, respectively. The enzymatic digestibility is related with the removal of lignin and hemicelluloses.