The electrooxidation of methanol on Pt-Ru catalyst supported by basal. plane graphite was investigated in phosphoric acid solution by cyclic voltammetry, X-ray diffraction (XRD) and scanning electron microscope (SEM). Pt-Ru catalysts were prepared by applying a potential of 0.0 V in chloroplatinic acid solution of various ruthenium chloride concentrations. The peak potential of methanol oxidation is shifted to a lower potential as the concentration ratio df Ru/Pt in the electrodeposition solution. Shifts of peak potential are due to the difference of the oxidation pathway of CO adsorbed on the surface of Pt-Ru catalyst. For methanol oxidation in phosphoric acid solution, the electrocatalytic activity of the catalyst prepared in ruthenium chloride solutions of chloroplatinic acid solution (1:1) was better than that of catalysts prepared in different concentrations of ruthenium chloride solution.