One among important factor for the design of reactor for a preferential oxidation of CO in fuel processor for PEMFCs is the management of the heat of reaction to gain a high CO conversion. Although the microchannel reactor has an advantage; i.e. fast heat transfer rate, there are difficulties accompanying the handling of heterogeneous systems in microchannel reactors, such as adhesion and particle adsorption. In our work, oxidizing the CO over the powder of Pt catalyst in hybrid MCR which composed minichannel reactor and microchannel heat exchanger has been developed. It is obvious that hybrid MCR might be better on the management of heat than the fixed bed reactor in spite of using the powder of Pt catalyst. CO conversion above 90% in hybrid MCR at GHSV=30,000hr-1 and O2/CO=1.0 was shown in the wide rage of reaction temperature (170-250oC) and CO conversion was reached at 99.9% at O2/CO=2.0.