Steam reforming (SR) of pure butanol and a specific mixture (butanol/acetone/ethanol = 6/3/1, mass ratio) assumed as a model of bio-butanol raw mixture have been researched over mesoporous MgO supported Ni catalysts with various particle size (3.6-8.8 nm). The catalysts were characterized by N-2 adsorption, H-2-TPR, XRD, XPS and TEM. The volcano-like curves were observed when the H-2 yield and H-2 selectivity were plotted as a function of the nickel particle size in butanol steam reforming (BSR) and acetone butanol ethanol steam reforming (ABESR) reactions. Prepared mesoporous Ni-0.12/MgO catalysts exhibited the highest catalytic performance in two model reaction systems. Surprisingly, the Ni particle size effects in BSR developed difference with counterpart in ABESR. Specifically, the catalytic performance of mesoporous Ni-0.20/MgO even outperform that of mesoporous Ni-0.08/MgO catalyst with respect to lower by-products selectivity and higher hydrogen yield in ABESR compared to BSR results. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.