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.