In this work, we prepared carbon-supported tin oxide-decorated platinum (SnOx-Pt/C) nanocatalysts using a scalable impregnation method. SnOx on the surface of the SnOx-Pt/C nanocatalysts do not cause significant activity decay because of its low content (< 10 at%). The mass activity of the SnOx-Pt/C catalyst with 10 wt % Sn is determined to be 150 mA/mgPt and the electrochemical active area is 69.3 m 2 g -1 . Electrochemical half-cell tests reveal that there is no significant lose in the mass activity (< 30%) and the electrochemical active area (< 20%) after 40,000 cycles between 0.6 and 1.2 V. In contrast, the mass activity of Pt/C catalysts under the same conditions decayed by 40% and the active area decreased by 70%. More importantly, in the membrane electrode full cell test, after the square wave potential cycling test at 0.6 and 1.0 V for 10000 cycles, the mass activity of SnOx-Pt/C catalyst decayed by 19%, while the Pt/C decayed by ~77%. The atomic surface and electron structure were accurately analyzed by spherical aberration electron microscope and X-ray absorption spectroscopy, where the surface tin oxides modulate the Pt electron structure. Combined with surface valence state analysis and electrochemical tests, it is found that the oxygen-containing species are preferentially adsorbed on the surface tin atoms, which then attenuates the adsorption of these intermediates on Pt surface. This effect not only optimizes the catalytic reaction path of hydroxyl, but also inhibits further oxidation of Pt nanoparticles, thus improving the stability of the SnOx-Pt/C nanocatalyst.