We prepared various Ru catalysts supported on different supports such as yttria-stabilized zirconia (YSZ), ZrO2, TiO2, SiO2 and gamma-Al2O3 with a wet impregnation method. We applied them to the selective CO removal in a hydrogen-rich stream via the preferential CO oxidation (PROX) and the selective CO methanation simultaneously. Among them, Ru/YSZ showed the highest CO conversion especially at low temperatures. Several measurements: the N-2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), the CO chemisorptions, the temperature-programmed oxidation (TPO), the temperature-programmed reduction (TPR). the temperature-programmed desorption (TPD) of CO2 with mass spectroscopy and the transmission electron microscopy (TEM), were conducted to characterize the catalysts. No linear correlation can be found between the amount of CO chemisorbed at 300 K and the PROX activity. On the other hand, the facile activation Of O-2 appeared to be closely related to the high PROX activity, judging by the TPO experiment. In addition, the strong adsorption Of CO2 suppressed the low-temperature PROX activity. Ru/YSZ can be easily oxidized and also reduced at low temperatures. It is found that Ru/YSZ uptakes only small amounts Of CO2, which can be desorbed at low temperatures. Ru/YSZ can reduce the high inlet CO concentration to be less than 10 ppm even in the presence of H2O and CO2. (C) 2009 Elsevier B.V. All rights reserved.