Acetic acid (AC) is a representative compound of bio-oil via fast pyrolysis of biomass, and can be processed for hydrogen production via steam reforming (SR). In the current work, the NixCo1-xMg6O7 +/-delta (x = 0-1) bimetallic catalysts were prepared via co-precipitation and impregnation, and tested in SR of AC. The reaction results indicate that the monometallic catalysts were deactivated obviously in SR, while the Ni0.2Co0.8Mg6O7 +/-delta bimetallic catalyst performed better in both activity and stability: not only the conversion of AC remained stable near 100%, but also the H-2 yield maintained stable near 3.1 mol-H-2/mol-AC. The results of XRD, BET, XPS, TG and TEM indicate that the high catalytic performance of the Ni0.2Co0.8Mg6O7 +/-delta catalyst can be attributed to 1) resistance to oxidation of active metals, 2) resistance to coking, and 3) stability of structure and electronic properties. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.