Co-deoxy-liquefaction of biomass and vegetable oil was investigated under the conditions of different temperatures (350-500 degrees C) and residence time as well as catalyst using HZSM-5. Results suggested low temperature was favorable for the formation of diesel-like products, while high temperature caused more gasoline-like products. By the addition of HZSM-5, at 450 degrees C alkanes content of the obtained oil with low oxygen content of 2.28%, reached a maximum of 56.27%, resulting in the highest HHV of 43.8 MJ kg(-1). High temperature favored cracking activity of HZSM-5 which reduced the char formation and contributed to the removal of carbonyl. Compared to temperature, the effect of residence time on products was relatively less: experiments indicated the optimum residence time was 15 min at which obtained oil with the highest yield of 17.78%, had better properties. Preliminary analysis of mechanisms showed biomass provided hydrogen for vegetable oil, facilitating hydrogenation of C=C bonds of vegetable oil. (C) 2010 Elsevier Ltd. All rights reserved.