Abstract: The reduced pressure distillation of bio-oil and the ethanol with the mixing ratio of 2:3 by weight were subjected to catalytic co-cracking over ZSM-5/MCM-41 molecular sieve in a fixed-bed reactor. The effects of reaction temperature and WHSV on cracking products were investigated. The catalyst is characterized by NH₃-TPD, BET, N₂ adsorption and desorption. The gaseous products were analyzed by gas chromatograph, and reduced pressure distillation of bio-oil and the upgraded bio-oil were quantified by gas chromatograph-mass spectrometry. It is found that the optimum conditions for the upgrading of bio-oil are 500 ℃ of the reaction temperature and 3.75 h^-1 of the WHSV, under which the acid substance in upgraded bio-oil is markedly reduced from 25.6% in reduced pressure distillation of bio-oil to 0.1% after upgrading. Meanwhile, the yield of upgraded bio-oil is 46.8%, and the concentration of CO₂ and CO in the gaseous products is 9.5%.