The effect of solvents (water and ethanol) on liquefaction characteristics of rice stalk (RS) was investigated in an autoclave. The highest conversion and liquid yield in water and ethanol were 84.95 wt%, 72.62 wt% and 78.93 wt%, 63.84 wt%, respectively. FTIR and GC-MS of the bio-oils obtained from subcritical water (SubH(2)O, 300 degrees C) and supercritical ethanol (scEtOH, 300 degrees C) indicated that the behavior of RS liquefaction depended on solvents used. The major components of bio-oil produced in SubH(2)O were ketones and phenols, while esters and phenols dominated in scEtOH. ICP-OES analysis showed that the concentrations of potassium (K) and sodium (Na) in the bio-oil obtained from scEtOH were 14-15 times higher than that obtained from SubH(2)O. Ethanol gave rise to an improvement in the bio-oil properties including water content, density, acidity and HHV. It was concluded that the bio-oil from RS can be effectively upgraded in scEtOH. (C) 2015 Elsevier Ltd. All rights reserved.