The decomposition of methane for hydrogen production over a Co-Mo catalyst with 25% Co loading carbided at various temperatures was studied at 973 K and atmospheric pressure. The 700 K-carbided catalyst was the most active of the other catalysts for H-2 production (above 98%) in the decomposition at 44 h. The Co-Mo catalysts carbided at 725 and 750 K were also active at 44 h, while the catalyst carbided at 800 K was active for I h but quickly deactivated. The catalysts carbided at 873 and 973 K were less active. The XRD analysis showed that the catalysts carbided at 700-750 K consisted Of MoO2 and CoMoO4 which were turned to CoMoOxCy, beta-Mo2C, and Co metal during the CH4 decomposition. The carbiding at 800 K produced CoMoOxCy which changed to beta-Mo2C and Co metal after the reaction. The carbiding at 873 and 973 K contained beta-Mo2C and Co metal. The effects of two carbiding methods of different heating rates, H-2 pretreatment, and CO2 addition on the catalytic activity and hydrogen production were studied.