Abstract: In this study, compositions and inhibitors of steam pretreated corn stover with acetic acid impregnation were analyzed. Enzymatic hydrolysis and simultaneous saccharification fermentation of corn stover pretreated at corresponding situation were investigated. The results show that acetic acid impregnated corn stover can be steam exploded at relatively low temperature that is profitable to increase the hydrolysis rate of hemicellulose and the recovery of xylose. The enzymatic hydrolysis experiment showed that when corn stover was impregnated with 1.0 % HAc at 200 ℃ for 10 min, a glucose yield of 284 mg per 100 g corn stover, corresponding to 76.8 % of theoretical maximum, was obtained. After 96 h SSF,the end ethanol concentration is 22.5 g/L, corresponding to 72 % of the theoretical value. It is 11.9 percent point higher than that without acetic acid impregnation.