Development of nonprecious metal-based catalysts highly active for complete oxidation of CH4 at a temperature <= 600 degrees C is significant for removing unburned CH4 at exhaust of engines of vehicles using natural gas or liquefied petroleum gas. CeO2 is active for complete oxidation of CH4. Co3O4 has been identified as a promising catalyst for this reaction. A Co3O4/CeO2 nanocomposite catalyst consisting of ceria nanorods supported on Co3O4 nanoparticles was prepared through a modified deposition precipitation method. The Co3O4/CeO2 nanocomposite exhibits high activity for complete oxidation of methane with an apparent activation energy of 43.9 kJ/mol, which is obviously lower than 95.1 kJ/mol of pure CeO2 and 89.7 kJ/mol of pure Co3O4, suggesting a synergetic effect between Co3O4 and CeO2. Surface of the Co3O4/CeO2 nanocomposite during complete oxidation of CH4 in the temperature range of 200 500 degrees C and potential stable intermediate of this catalysis were identified with ambient pressure X-ray photoelectron spectroscopy (AP-XPS).