The SiW12 modified Pt electrode was prepared by a cyclic voltammetry scan in H2SO4 containing SiW12. During the preparation of modified electrode, we found a redox reaction of SiW12 in hydrogen area on the Pt electrode, but the adsorption increasing for the particles containing Oxygen in Oxygen area on the electrode surface. The electrochemical behaviour of this modified electrode in H2SO4 and its electrocatalytic effect to methanol oxidation were studied by cyclic voltammograms and I-t curves of constant voltage. The results show that the Pt electrode modified by Silicatungstic acid has not only the higher catalytic activity to methanol oxidation, but also the effect decreasing CO poison.