Liquefaction co-catalyzed by Raney nickel and NaOH in isopropanol (2-PrOH)/H2O is an efficient method for transforming lignocellulosic biomass into bio-oil. The present study investigated the effect of reaction temperature, residence time, and dosage of the catalysts on the yield and composition of bio-oil. To understand the liquefaction mechanism, the transformation of lignin and cellulose at the same conditions was investigated as well. The results indicated that 240 degrees C was the optimum temperature in terms of bio-oil yield. It was also found that residence time had a great effect on not only the bio-oil yield but also the composition and higher heating value (HHV) of the bio-oil. Increasing the dosage of the catalysts also improved the yield and HHV of bio-oil. Most phenols in bio-oil were originated from lignin, while most ketones and hydrocarbons were produced by cellulose.