In a study of the preparation of Pt/C eletrocatalysts, a set of modified Vulcan XC-72 carbon black supports have been prepared by nitric acid or hydrogen peroxide oxidation, or thermal treatment in nitrogen flow. The supports obtained by these methods had largely identical pore structure, but different from the amount of surface oxygen-containing groups. The physical and surface chemical nature of the supports was characterized by XPS, BET, FTIR, and acid-base titration. The above pre-treatment-carbon supported Pt/C electrocatalysts were prepared by the impregnation-reduction method with formaldehyde as the reducing agent, H2PtCl6 as precursor. The effect of the amount of surface oxygen-containing groups of Vulcan XC-72 carbon black on the Pt/C catalysts dispersion was studied by the characterization with XRD and TEM. It was discovered that decreasing the amount of surface oxygen-containing groups on carbon supports favored the dispersion of platinum on the Pt/C catalysts.