Abstract: Ag@Pt core-shell nanoparticles(Ag@Pt NPs) composed of an Ag nanoparticle core and a Pt shell were prepared by the seed-mediated growth method and self-assembly technology. The electrocatalytic properties of Ag@Pt NPs to methanol before and after invalidation were measured and compared during the electrocatalytic process. The invalidation mechanism was studied by transmission electron microscopy,high-resolution electron microscopy,and X-ray photoelectron spectroscopy. The results show that the cavitation phenomena of Ag@Pt NPs occur during the cyclic voltammetry process with a threshold voltage of 0.5 V and become more obvious with the increase of time. Ag@Pt particles turn into Pt hollow shells coated by Ag after cavitation,which is the reason that the catalytic property of Ag@Pt NPs to methanol distinctly decreases during the electrocatalytic process.