The invention relates to the technical field of petrochemical industry, in particular to a carbon monoxide combustion improver and a preparation method thereof. In the carbon monoxide combustion improver and based on the total weight of the combustion improver, the loading capacity of an active component platinum is 0.01 to 0.1 percent, the loading capacity of magnesium oxide is 0 to 5 percent, the loading capacity of cerium oxide is 0.5 to 6 percent, the loading capacity of lanthanum oxide is 1 to 10 percent, and the rest is a carrier; the carrier is an activated aluminium oxide microsphere. The carbon monoxide combustion improver is prepared by a spray drying method. By adoption of the carbon monoxide combustion improver and the preparation method thereof, the dispersion rate and the utilization rate of the active component are increased, the increasing amplitude of NO in flue gas can be controlled effectively while the CO content is reduced, and environmental friendliness is achieved.