Liquefaction of sawdust was studied in methanol-water solutions using an acid catalyst under microwave energy. The effect of the methanol concentration on the changes of components in the liquefied products was analyzed by gas chromatography-mass spectrometry (GC-MS). It was found that 5-hydroxymethylfurfural (HMF) and levulinic acid are the dominate products using pure water as the liquefying agent. These two important intermediates are decomposed from glucose by the acid catalyst. When the concentration of the methanol was increased from 0 to 50%, the percentages of HMF and levulinic acid were dramatically decreased from 16.67 and 39.16% to 2.36 and 2.71%, respectively. At the same time, the total content of sugar derivatives increased to 56.96%. This result indicated that methanol could not only improve the conversion of biomass but also promote the stability of the sugar derivatives from further decomposition to carbonyl compounds, such as HMF and levulinic acid. Therefore, a potential polyol product was obtained by a liquefaction reaction using lignocellulosic materials.