Abstract: In this study, a new green detoxification technology named-ionic liquid extraction was used for detoxification of the prehydrolyzate obtained from the washed acid-catalyzed steam-exploded corn stover in order to improve the ethanol fermentability of yeast. 1-butyl-3-methyl imidazole hexafluorophosphate(C4mim PF6) was selected as the extraction agent and its extraction conditions had been optimized. The optimal extraction conditions were as follows:the ratio of aqueous to organic phase 1:2, 35℃, 250 r/min, and 60 min. Under these conditions, the removal rate of formic acid, acetic acid, levulinic acid, 5-hydroxymethylfurfural, furfural and total phenols in the hydrolysate reached 24.72%, 21.84%, 47.99%, 82.76%, 100% and 39.7% respectively, the extraction efficiencies of the main inhibitors were high and the loss of sugars was negligible. The results of detoxification mechanism indicated that the extraction efficiency of the inhibitors decreased with the increase of alkyl chain length on the cation of ionic liquidCnmim PF6 (n=4, 6, 8); the more hydrophobic the inhibitors were, the stronger the hydrogen bonding with ionic liquid was; the lower the pH value was, the better the extraction efficiency of inhibitors was.The removal rate of acetic acid, 5-hydroxymethylfurfural and 4-hydroxybenzaldehyde inC4mim PF6 did not change with the initial mass concentration of inhibitors.