Partial dissolution of corn stover in ionic liquid (IL) was employed for pretreating biomass and achieving enhanced glucose and xylose yield. The xylan recovery in solid fraction after IL pretreatment decreased as temperature increased. Xylose yield was significantly increased at a relatively low temperature (110 degrees C) compared with the high-temperature (over 130 degrees C) pretreatment, which resulted in a significant xylan degradation. A maximum total sugar yield of 88.0%, with glucose yield of 93.9% and xylose yield of 75.9% based on untreated biomass, was obtained at 110 degrees C for 3 h pretreatment without complete dissolution of biomass. A sugar yield of 78.0% was obtained with IL pretreatment at 70 degrees C for 24 h. Synchrotron wide-angle X-ray diffraction was employed to investigate the crystalline structure of biomass. Both cellulose crystallinity and remaining lignin amount were correlated with cellulose digestibility. (C) 2012 Elsevier Ltd. All rights reserved.