To effectively improve the enzymatic digestibility of carbohydrates in lignocelluloses, the combined hydrogen peroxide and liquid ammonia treatment (H-LAT) was employed as pretreatment for corn cob. The effects of temperature and H2O2 loading on solid recovery, enzymatic digestibility and lignocellulosic structure of corn cob were investigated. The results showed that the H-LAT pretreatment could effectively remove lignin and retain the most of carbohydrate in the corn cob. Enzymatic hydrolysis using cocktail enzymes including cellulase, β-glucosidase and xylanase for 72h after pretreatment under optimal conditions, the H-LAT pretreatment achieved 85.0% of theoretical sugar yield, and it could produce 593.1g fermentable monosaccharide per kilogram of dry biomass. Compared with untreated substrates, it was about 3.53 fold in sugars yields for H-LAT treated substrates. X-ray diffraction analysis showed that the crystalline region and amorphous region of corn cob were synchronously decreased; the crystallinity changes were depended on the interaction of the two effects. Infrared spectrum analysis showed that the H-LAT pretreatment effectively broke down cellulose hydrogen bonds, and disrupted ester linkage in lignin-carbohydrate complexes. Meanwhile, lignin molecular structure was partly destructed, and the distribution of lignin produced certain changes. As a result, these changes effectively reduced the biomass recalcitrance of corn cob.