Abstract: Hydrogen production from ethanol steam reforming has been investigated over nickel catalysts with respect to the nature of the support, the metal loading and calcination temperature. It was found that the Ni/CeO2 catalyst with Ni loading of 15% is more active and selective toward hydrogen production. Increasing the calcination temperature results in the agglomeration of NiO and CeO2 particles, and consequently decreases the reforming ability of the catalyst. Namely, smaller particles favor the ethanol steam reforming, while larger NiO and CeO2 particles promote the decomposition of ethanol. Mechanistic study by adding CO, CO2 and CH4 to the reaction stream at 350℃ further suggests that methane is produced by the direct decomposition of ethanol and/or acetaldehyde, instead of the methanation reactions of CO and CO2.