The application of a novel Ce0.5Zr0.5O2 mixed oxide prepared by the microemulsion method as a support of Ru catalysts for the reforming of CH4 with CO2 originates a high-activity catalytic system with excellent stability under reaction conditions. The support characteristics clearly determine the catalytic stability of Ru catalysts under CH4 + CO2 reaction conditions. The introduction of cerium as a promoter in the ZrO2 structure is shown to improve the catalyst performance by increasing the oxygen mobility in the support and consequently reducing deactivation by carbon deposition during reaction.