The compositions of five different monosaccharides in corn stalk enzymatic hydrolysate were analyzed by HPLC. They were arabinose, mannose, galactose, glucose and fructose, in which glucose and fructose were the main compositions.The results showed that the reducing sugar composition contents in corn stalk powder with a particle ＞1 200 mesh was higher than that with a particle size 100～200 mesh. The content of arabinose, galactose, glucose, mannose and fructose in enzymatic hydrolysate with particle size of ＞1 200 mesh increased 48.38%、64.29%、37.63%、70.07% and 22.34%, respectively. In addition, three new unknown response peaks occurred in the chromatograms, which might be fucose, sucrose and cellobiose.