As revealed in Table 2, the addition of NaOH catalyst in the liquefaction process further increased the content of carbon and hydrogen in bio-oil but reduced the concentration of oxygen. The results quoted above may be accounted for by the enhanced hydro-cracking and hydrogenation reactions. In other words, the dehydration reactions were improved and the formation of CO/CO2 was relatively weakened (by using NaOH as catalyst). Therefore, the bio-oil obtained with NaOH as catalyst had a higher caloric value compared with that produced without catalyst.