A novel Ni/Mg-Al-O catalyst has been successfully synthesized by the cation-anion double hydrolysis (CADH) method for carbon dioxide (CO2) reforming of methane. Compared with the Ni/MgO-Al2O3 catalyst prepared by the conventional co-impregnation method, the Ni/Mg-Al-O catalyst exhibited enhanced initial activity and improved long-term stability. Structural characterizations revealed that higher metal dispersion (2.8 times) and better intrinsic activity (1.8 times in terms of turnover frequency at 700 degrees C) were achieved by ultrasmall Ni nanoparticles (2.1 nm) on the Ni/Mg-Al-O catalyst, leading to the enhanced initial activity. The improved long-term stability of the Ni/Mg- Al-O catalyst was attributed to the superior anti-coke property, which was rationalized by the ultrasmall Ni nanoparticles and abundant basic sites. The present work provides a facile and green method for the synthesis of efficient reforming catalysts and elucidates the mechanisms underlying excellent catalytic performances.