Cu-CeO2 catalysts were prepared by co-precipitation and liquid phase oxidation (CP-LPO) and the prepared catalysts were examined as selective oxidation of carbon monoxide catalysts for the application of fuel cell vehicles. The prepared Cu-CeO2 catalysts showed high reaction activity, but it was hard to find the correlation between the amount of Cu loaded and the reaction activities. As increase of the amount of Cu loaded, the micro pore structure of the catalyst was changed. It is due to the formation of solid solution between Cu and CeO2. During pretreatment, the catalyst formed the solid-solution of Cu-Ce-O, resulting in the improvement of catalytic activity.