AbstractSteam explosion pretreatment of wheat straw can solubilize a significant portion of the hemicellulosic component and enhance the enzymatic digestibility of the remaining cellulose for fermentation into ethanol. In this work, wheat straw was pretreated by steam explosion using different steam temperatures and retention times, and the chemical compositions of the raw and steam-exploded wheat straw were analyzed. Results showed that the content of hemicellulose decreased sharply at higher steam temperatures and longer retention times; however, the content of lignin changed inconspicuously. After pretreatment, the characteristics of the straw fiber were investigated by studying their proportion of microfibrils, SEM, and FTIR. To assess the differences among various pretreatment parameters, the concentration of the reducing sugar and glucose conversion were determined. The highest reducing sugar concentration and glucose conversion were achieved at the explosion conditions of a pretreatment temperature of 220 ºC and a residence time of 3 min.