Mixed metal oxides with hybrid structures often show synergistic effects and thus much better catalytic properties than their single components. We present here the synthesis of Ce/Co mixed oxalates via a facile co-precipitation method, and the following calcination process resulted in the final CeO2/Co3O4 hybrid microstructures. Then the systematical characterizations were conducted to study their structure evolution and composition-dependent properties on catalytic CO oxidation. The results show that the hybrids of CeO2/Co3O4 were composed of 5 nm sized CeO2 and 20 nm sized Co3O4. While increasing the feeding amount of Ce, the morphologies of the as-obtained CeO2/Co3O4 hybrids changed from the flower-like microstructures to the hot dog-like ones, and finally to the sheet-like ones. After catalytic tests, it was found that the CeO2/Co3O4 hybrids show different catalytic activities by varying the molar ratios of Ce/Co (pure Co for Co-oxalate, Ce/Co = 1/19 for Ce-1/Co-19-oxalate, Ce/Co = 1/9 for Ce-1/Co-9-oxalate, Ce/Co = 3/7 for Ce-3/Co-7-oxalate, Ce/Co = 5/5 for Ce-5/Co-5-oxalate, pure Ce for Ce-oxalate). Among these samples, Ce/Co = 1:19, which has a higer pore volume performed the optimal catalytic property compared to the others. (C) 2016 Elsevier Ltd. All rights reserved.