Controlling the size of Pt nanomaterials can be an effective route to improve their catalytic activity on a mass basis for the reactions of direct methanol fuel cell (DMFC).Herein we demonstrated the synthesis of ultrafine platinum nanoclusters based on the replacement reaction between Ag nanoparticles and Pt(Ⅳ) precursors.All the reactions were performed in the presence of commercial carbon powders, the Pt/C thus formed could be directly used for catalyzing the DMFC reactions.By comparison with the commercial Pt catalysts from E-Tek, the Pt nanoclusters exhibit superior catalytic activity toward the methanol oxidation and oxygen reduction, the two key reactions in direct methanol fuel cell, due to the relative smaller Pt sizes.