In the traditional corn stover cellulose separation process, it is generally treated with strong acid such as sulfuric acid, which has strong acid corrosion and large alkali consumption. Based on this, the treatment of phosphoric acid pretreatment combined with alkaline hydrogen peroxide was studied, and the changes of cellulose, hemicellulose and lignin contents in corn stover during the treatment were investigated. The optimum process was optimized by single factor experiments: phosphoric acid treatment temperature of 150℃, treatment time of 1.5h, phosphoric acid concentration of 1.67%, sodium hydroxide concentration of 1.0%, hydrogen peroxide concentration of 2.0%, treatment temperature of 50℃, treatment time of 3h, the yield of cellulose obtained from corn stalk under this condition was 89.02%, hemicellulose removal rate was 93.25%, lignin removal rate was 95.18%, the purity of the cellulose reached 90.19%. Meanwhile, a high secondary value product can be obtained in the filtrate obtained by the phosphoric acid treatment process, including xylose of 68.72%, arabicose of 65.14% and furfural of 30.25%. The characterization of the raw materials and the treated materials showed that the phosphoric acid treatment can effectively remove the hemicellulose and the alkaline hydrogen peroxide treatment can remove lignin components. The cellulose crystal form was not changed, but the crystallinity was increased significantly, and the thermal stability was increased. In addition to obtaining highpurity cellulose, the use of this preacid postbase treatment can also give high added value as a by-product of xylose and furfural. The research laid a theoretical foundation for the efficient utilization of corn stover cellulose.