Nanosized Au and Au-Pt bimetallic particles of different atomic ratios were synthesized from HAuCl4 and HPtCl6 inside the channels of amine functionalized MCM-41. These were characterized through chemical analysis, XRD and TEM. The size of the bi-metallic particles was found to be in the range of 2-4 nm. Their catalytic activities were evaluated in simulated gas mixtures that typically contain 0.5 and 0.96% CO in presence of large proportions (∼74%) of H2. The catalysts that contain higher concentrations of Pt were found to be active and offer good CO preferential oxidation activity. Catalysts that contain an optimum amount of Au along with Pt have shown highest activities at lower temperatures.