Abstract: A series of Ag/CeO₂-Co₃O₄ catalysts with various Ce/Co ratios were prepared by co-precipitation method and employed in the low-temperature oxidation of formaldehyde. The results demonstrate that the Ag/CeO₂-Co₃O₄ catalysts exhibit excellent performance in the oxidation of formaldehyde and the Ce/Co ratio has a significant impact on the catalytic performance. The XRD, nitrogen adsorption-desorption, Raman spectroscopy, H₂-TPR and in-situ DRIFTS results illustrate that with the increase of Co content in Ag/CeO₂-Co₃O₄, the pore volume increases whereas the surface area decreases. The presence of CeO₂ is beneficial to enhancing the redox ability and increasing the oxygen vacancies and Co²⁺ species, which can promote the activation of oxygen species and then the degradation of formaldehyde. According to the in-situ DRIFTS results, the decomposition of formates on the catalyst surface is probably the rate-determining step for the degradation of formaldehyde at low temperature.