Effects of alkali metals on nickel catalysts for carbon dioxide reforming of methane were studied. For Ni/γ-Al₂O₃ catalysts made by liquid-phase oxidation, which exhibited greater activity and resistances to sintering and to coke formation during the reaction, the doping of alkali metals like lithium enhanced the ability to remove the coke. For the catalysts made by liquid-phase oxidation, the coke moved from nickel to the support and reacted with carbon dioxide producing the desorbing CO. Doped lithium made the weak acidic γ-Al₂O₃ relatively basic, promoted the adsorption of carbon dioxide, and as a result, reduced the amount of coke deposited on the catalysts. Nickel catalyst supported on TiO₂, another acidic metal oxide, showed a remarkable reduction of coke deposition by the addition of lithium.