Abstract: The bio-oil produced by fast co-pyrolysis of municipal sewage sludge and typical wooden biomass（pine sawdust and poplar sawdust） in a horizontal tubular furnace was studied.The yield and composition of bio-oil generated during co-pyrolysis process were further analyzed.The results show that the bio-oil has similar components with the two biomasses,which mainly contains acids,esters,phenols,and nitrogen compounds.Higher amount of biomass can reduce sulfur content in the bio-oil but promotes the accumulation of nitrogen.Synergistic effect on bio-oil yield is calculated,and the result indicates that synergistic effect has negative correlation with high sawdust addition rate.The greatest synergistic effect on the bio-oil yield,which is 12.12%,is observed when 10% poplar sawdust is added.