Hydrolysis of cellulose by hot-compressed ethanol/water mixture it; a promising way to obtain reducing sugar (RS) for biofuel production. The purpose of this research is to obtain high RS yield. In this work, the hydrolysis of microcrystalline cellulose by batch hot-compressed ethanol/water mixture was investigated. The influence of the ethanol/water mixture density corresponding to temperature and pressure on the RS yield was further examined. The hydrolysis conditions were optimized for high sugar yield and the crystallinity indexes (Cl) of the residue and the original cellulose were analyzed. The RS yield reached as high as 98.22% under the conditions of ethanol mole fraction of 0.22, temperature of 260 C, pressure of 5.75 MPa, reaction time of 35 s, and stirring speed of 10 Hz. The IR crystallinity index of cellulose was decreased to 0.211 from 0.618. It is shown that the RS can be produced effectively by cellulose hydrolysis in hot-compressed ethanol/water mixture. (C) 2012 Elsevier Ltd. All rights reserved.