The effect of AlCl3 on hydrolysis of microcrystalline cellulose in high temperature liquid water (HTLW) has been investigated. The results show that AlCl3 can accelerate the hydrolysis of cellulose and the decomposition of glucose simultaneously. It can reduce the hydrolysis temperature and increase the content of glucose within short residence time. Extremely low AlCl3 can notably enhance the conversion of cellulose. By adding 0.01% AlCl3, the conversion of cellulose increases from 40.44% (without catalyst) to 86.79%, and the content of glucose in the product increases from 25.88% (without catalyst) to 64.46% at 260 degrees C, 2 min and 5.2 +/- 0.2 MPa. As an acid catalyst, AlCl3 can inhibit the isomerization and the retro-aldol condensation, and accelerate the dehydration of glucose. (C) 2011 Elsevier Ltd. All rights reserved.