Bimetallic nanoparticles (NPs) are widely used in energy catalysis, chemical synthesis, and chemical/biosensing, but their performance at single NPs level is still needed to investigate. In this work, bimetallic Au@Pt/Au NPs with triple-layered core-shell structure was successfully prepared and characterized. The single bimetallic Au@Pt/Au NPs were immobilized on the surface of Au nanoelectrode through electrostatic adsorption. The results have showed that the single Au@Pt/Au NPs have size-dependent properties for voltametric response and electron-transfer rate, and exhibit excellent electrocatalytic activity, long-term tolerance and anti-toxicity compared with the traditional Pt catalyst. This work provides new insight into conventional electrocatalysis and will likely give a good platform for designing entirely new catalysts at single NPs level.