Anodic treatment of PtRu/C catalysts in 0.5 M sulfuric acid at 1.3 V (vs RHE) for 0.5 h was found able to promote the activity for methanol oxidation by a few tenths to 5 times. This anodic activation effect was valid for samples domestically prepared under different conditions and that produced by Johnson-Matthey. On the basis of the changes of cyclic voltammetry during the anodic treatment, a model was proposed for the activation effect. According to the model, there are two categories of ruthenium oxides in the catalyst: one is electrochemically reversible and beneficial for catalytic activity, while the other is irreversible and harmful. During the anodic treatment, the harmful oxide is decreased, while the beneficial oxide either increased or changed only slightly, resulting in a beneficial net change.