An innovative reference approach was developed to investigate the solvent effects on the liquefaction of sawdust by using tetralin as a chemical probe, and the corresponding solvent impact index was defined in this study. The influence of reaction conditions including reaction temperature and solvent types on solvent impact index were discussed. It was found that larger solvent impact index corresponds to improved sawdust conversion and higher bio-oil yield. The liquid and gaseous products obtained were characterized by H-1 nuclear magnetic resonance (H-1 NMR), gas chromatography (GC), and elemental analysis (EA). The component of products highly depended on the employed solvents. (C) 2015 Elsevier Ltd. All rights reserved.