A facile, rapid and green method based on potentiostatic electrodeposition is developed to synthesize a novel H₃PMo₁₂O₄₀-Pt/reduced graphene oxide (denoted as PMo₁₂-Pt/rGO) composite. The as-prepared PMo₁₂-Pt/rGO is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results reveal that graphene oxide (GO) is reduced to the rGO by electrochemical method and POMs clusters are successfully located on the rGO as the modifier. Furthermore, the PMo₁₂-Pt/rGO composite shows higher electrocatalytic activity, better tolerance towards CO and better stability than the conventional pure Pt catalyst.