A novel catalyst Ir-FeO (x) /Al2O3 designed for the preferential oxidation (PROX) of CO under excess hydrogen was developed in this work. To clarify the promoting role of Fe species, three different impregnation sequences were employed, and the resultant catalysts were characterized by various techniques. The results showed that the Ir-FeO (x) /Al2O3 catalyst, which was prepared by the co-impregnation procedure, exhibited the best performance for the PROX. The partially exposed and highly dispersed Ir sites and the FeO (x) sites allowed good adsorption for both CO and O-2 over the Ir-FeO (x) /Al2O3, which was believed to be responsible for the enhanced activity.