Abstract: Using potential sweep and potential-time sequence techniques, we have studied the promotion of the UPDof lead for the electrocata-lytic oxidation of formic aeid on platinum in the HClO₄ aqueous solution.The results show that the first oxidation peak in the anodic direction and the oxidation peak in the cathodic direction in the cyclic voitammogram are attributed to the oxid-ation of the same weakly adsorbed intermediate, while the second and third oxidation peaks in the anodic direction are attributed to the oxidation of the two different strongly adsorbed intermediates.Furthermore, all these intermediates appear as the linear adsorption on the platinum surface and they are probably single bonded species, Pt-HCOO, and multiple bonded species, Pt=COand Pt=COH, respectively.So the function of the UPDof lead for the electro-oxidation of formic acid is neither a third-body effect nor the decrease of nydrogen adsorption thus preventing the formation of poisoning species.The role of the UPDof lead should be an electronic effect, that is, it modifies the adsorption property of platinum in such a way that the oxidation of Intermediate, Pt-HCOO, becomes easier.