The oxygen reduction reaction (orr) on carbon-supported Pt and Pt3Fe alloy has been studied by means of the ab initio and density function theory approaches. A model cluster consisting of substrate carbon atoms, Pt and/or Fe atoms on the three major crystal planes (100), (110) and (111) of Pt and Pt3Fe, was applied to simulate the carbon-supported-catalyst behavior. The anchor effect of iron to platinum on carbon has been confirmed from quantum chemistry. The enhanced catalysis effect of Fe in Pt/Fe ally catalyst on the orr has also been confirmed by the evidence disclosed in analysis of the frontal molecular orbital energy and the change of the O/O bond.