Upgrading of bio-tar derived from fast pyrolysis of sawdust was performed over activated charcoal supported nickel-based catalysts (Ni/AC, NiMo/AC, MgNiMo/AC) under supercritical ethanol conditions. The catalytic activities of the catalysts was compared with those of representative bio-oil upgrading catalysts (Ru/AC, HZSM-5). The MgNiMo/AC catalyst exhibited the highest catalytic performance among the catalysts with a decrease of oxygen content in bio-tar from 31.3 wt% up to 10.8 wt% and the yield of liquid product (75 wt%). The effects of reaction temperature (275-350 degrees C), reaction time (0-120 min) and bio-tar to ethanol ratio (1/9-4/6) were also studied over the MgNiMo/AC catalyst. In addition, reaction of vanillin which is one of major compounds present in bio-tar was carried out under the same bio-tar upgrading conditions in order to understand the production mechanism of phenolic chemicals.