The effects of Y2O3-modification to Ni/gamma-Al2O3 catalysts on autothermal reforming of methane to syngas were investigated. It was found that the introduction of Y2O3 (5%, 8%, 10%) lead to significant improvement in catalytic activity and stability, and the H-2/CO ratio could be adjusted via controlling the O-2/CO2 ratio of the feed gas. According to the characterization results of catalysts before and after reaction, it was found that the Y2O3 center dot gamma-Al2O3 supported Ni catalysts had higher NiO reducibility, smaller Ni particle size, higher Ni dispersion and stronger basicity than those of the Ni/gamma-Al2O3 catalysts. The analysis of catalysts after reaction showed that the addition of Y2O3 inhibited the Ni sintering, changed the type of coke and decreased the amount of coke on the catalysts. All the experimental results indicated that the introduction of Y2O3 to Ni/gamma-Al2O3 resulted in excellent catalytic performances in autothermal reforming of methane, and Y2O3 played important roles in preventing metal sintering and coke deposition via controlling NiO reducibility, Ni particle size and dispersion, and basicity of catalysts. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.