The available global kinetic expressions for gas-phase CO oxidation have been shown to be of insufficient accuracy in the nide temperature range that exists in many modern combustion systems. A simplified formula for the kinetics of CO oxidation in the presence of water vapor is here developed to cover the whole temperature range of 973-1673 K. Comprehensive kinetic calculations with a validated, elementary reaction mechanism serve at ideal plug flow conditions as a basis for the development work of the simplified mechanism. It is shown, in contrast to the simplified rate equations in the literature, that this new simplified model can predict the oxidation rate fairly well both at low and high temperatures.