biomass is one of the important renewable energy. more attention has been paid on conversion of biomass and the upgrading of its products. in this paper, the bio-oil was prepared by pyrolysis of pine sawdust in fast pyrolysis installation. a series of ruthenium catalysts were prepared for the upgrading of bio-oil. the catalytic activity was evaluated by the reaction of the model compound (acetic acid) under 3 mpa hydrogen pressure. the effects of ru-loading and second metal addition on the catalytic activity were investigated. the 0.5ru/gamma-al2o3 catalyst with 0.5%co addition exhibited the highest activity, giving the highest conversion of acetic acid (30.98%). after upgrading over this catalyst, the properties of the pyrolysis bio-oil were improved. the content of the esters increased by 2-fold in the upgraded oil than in the raw one. the gc-ms spectrometry analysis showed that not only the hydrogenation but also the esterification happened in the bio-oil over the coru/gamma-al2o3 catalyst. results indicate that it is possible to improve the properties of bio-oil by hydrotreating and esterifying carboxyl groups. (c) 2011 elsevier ltd. all rights reserved.