Abstract: By means of the cyclic voltammograrn, the effects of upper potential and activation mode on the catalytic activity of two Pt/C catalysts prepared by the sulfurous route and the stannous method for methanol electro- oxidation were investigated. It is showed that different catalysts obtains different optimistical upper potentials in step-by step activation by changing upper potential. At the optimum upper potential, one-step activation is more effective than step-by step activation for the stannous Pt/C catalyst. Different activities obtained under different activation modes indicates that Pt is transformed into different states during different activation processes which endow the resultant catalyst with the distinct adsorption capability and rate for anions and water.