This study reported the influence of oxygen exchanging capability on catalytic activity of dry reforming of methane (DRM) over a small loading amount of Ru (0.10 wt%) onto ceria-zirconia (CZ). The as-prepared samples were characterised by a range of techniques, including N2 adsorption–desorption, XRD, TPR, and Raman spectroscopy. It was found that the reducibility of CZ sample was significantly increased in the presence of Ru, and it was primarily due to the increased degree of structural defects by the promotional effect of Ru. This effect in turn increased the oxygen mobility and further promoted the catalytic activity of CZ for DRM in the temperature range of 600 °C – 850 °C. Density Functional Theory (DFT) calculations confirmed the increased oxygen mobility from the increased structural defects. Therefore, high conversions of CH4 and CO2 were observed at 850 °C, ca. 100% and 96.8%, as well as a near stoichiometric H2/CO ratio of 1.06 with the very small amount of Ru (0.10 wt%) introduced.