Catalytic activity of CO oxidation reaction in relation to oxidation for an ordered AuCu intermetallic compound is studied. Oxidation performed at temperatures above 400 degrees C on the AuCu intermetallic compound leads to the formation of a composite consisted of Au and CuO, accompanied by a large increase in the surface area and signiticant enhancement of the activity. The oxidation performed at 600 degrees C yields a unique composite structure where an An layer is sandwiched by two porous CuO layers, revealing a maximum in the surface area and the activity. The porous CuO layer is found to be key factor dominating catalytic activity. We show in this study that the oxidation of the intermetallic compound AuCu is a novel and an effective way to prepare metal/oxide composite for catalyst. (C) 2007 Elsevier B.V. All rights reserved.