Superior activation of on 1 wt% Pt/TiO2 catalysts for the oxidation of CO was attained by loading a large amount of Fe-oxide (100 wt%) and TiO2. In situ IR spectra of CO proved that the structural transformation is brought about on the Pt-sites by loading of Fe-oxide, where predominant Pt-sites giving linear CO change to highly reactive bridge CO Pt-sites. In contrast, no transformation of the linear CO sites to the bridge CO sites takes place by loading of TiO2 but the environment of Pt-sites for linear CO is changed.