Supported CoMn/AC composite oxide catalysts were prepared by a typical impregnation method at different calcination temperatures. The prepared CoMn/AC catalysts were characterized, and the catalytic activity of the prepared supported CoMn/AC oxide catalysts was also investigated by the catalytic combustion of phenyl volatile organic compounds (VOCs) (benzene, toluene, and ethylbenzene). XRD and XPS results indicated that MnCo2O4 and CoMn2O4 were the main crystal phase species in the prepared supported CoMn/AC oxide catalysts. The active components were observed to be highly dispersed and had small crystal sizes. The toluene catalytic combustion results demonstrated that the CAT350 catalyst had higher toluene catalytic combustion activity than the CTA250, CAT300, and CAT400 catalysts. The toluene catalytic combustion conversion of the CAT350 catalyst exceeded 93.5% at 235 ℃, with a decreased toluene concentration in air of less than 130 ppm at 250 ℃. The order of toluene catalytic activity of the supported CoMn/AC oxide catalystswas as follows: CAT250 < CAT300 ≒ CAT400 < CAT350. The catalytic combustion activity and stability of the CAT350 catalyst also increased with the increase in reaction temperature. The catalytic activity of the CAT350 catalyst was investigated to bring about the complete oxidation of benzene, ethylbenzene, and toluene. The combustibility of phenyl VOCs on the CAT350 catalyst was observed to follow the order benzene < ethylbenzene < toluene. Therefore, the differences in the phenyl VOC catalytic combustion performances of the supported CoMn/AC composite oxide catalysts can be attributed to the different physical chemistry properties of the phenyl VOC molecules and the catalyst.