The effect of platinum loading on the performance of oxygen reduction over Ru-based cluster catalyst in acid electrolytes has been studied by rotating disk electrode. The Pt-Mo-Ru-Se catalysts were synthesized by low temperature method and characterized by XRD, EDS and XPS. The activities were measured by potentiodynamic and AC impedance techniques. The results show that Mo-Ru-Se catalysts doped with platinum were with greatly enhanced catalytic activity and methanol resistance and have higher current density and lower overpotential for oxygen reduction reaction than that of platinum-free Mo-Ru-Se catalysts under the same conditions. The Mo-Ru-Se catalyst with 5% Pt loading showed the best performance, and the peak current density was 213 mA•mg-1 in 0.5 mol•L-1 H2SO4 solution, approached 70% of the Pt activity and the initial oxygen reduction potential was-0.05V.