Co-doped LaAlO3 nanoparticles with partial reduction were applied as a catalyst to ethanol steam reforming. Co-doped LaAlO3 nanoparticles were prepared using chemical solution deposition. The Co component was generated on the nanoparticle surface by a partial reduction process. The estimated H-2 yield of the ethanol steam reforming process was changed by altering the reduction conditions, although the surface areas of the reduced nanoparticles were almost equal. The highest H-2 yield was attained at 948 K reduction temperature. The calculated H-2 yield and the conversion ratio were, respectively, 78% and 99%. Reaction bi-products during steam reforming were measured to elucidate the change of the H-2 yield with the reduction temperature. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.