The volumetric entropy generation rate distributions and exergy losses of fuel lean premixed CO/H-2/air flames are investigated numerically in a micro-scale cylindrical channel at atmospheric pressure. The numerical simulation predicts the gas properties such as temperature, density and species concentrations by the detailed gas phase chemistry and transport. The entropy generation rates due to the effects of chemical reaction, thermal conduction and mass diffusion are calculated based on the gas properties. A detailed parametric study of the influence of CO/H-2/air flow velocity and CO mass fraction on the volumetric entropy generation rate is performed. The entropy generation rate induced by chemical reaction is suppressed by adding more CO to the mixture. However, higher thermal conduction induced entropy generation is inspected in the mixture with more CO. The total entropy generation rate rises with the inlet velocity. This is the first systematical analysis of the volumetric entropy generation rates distributions of CO/H-2/air flames in the micro channel. The analysis could be applied to other power conversion systems which utilize CO/H-2/air mixture. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.