Developing　stable　and　high-performance　Pt-based　alloy　catalysts　is　essential　for　advancing　the　oxygen　reduction　reaction　(ORR)　in　proton　exchange　membrane　fuel　cells　(PEMFCs),　as　the　harsh　operating　conditions　often　cause　the　leaching　of　transition　metals.　Herein,　a　highly　stable　electrocatalyst　(Pt-Ce-N-C)　consisting　of　ultra-small　Pt-Ce　alloy　nanoparticles　and　atomically　dispersed　Pt-Nx　and　Ce-Nx　dual　sites　for　highly　efficient　ORR　is　reported.　The　Pt-Ce-N-C　demonstrates　a　remarkable　mass　activity　(MA)　of　1.17　A　mgPt-1,　7　times　higher　than　that　of　commercial　Pt/C.　Importantly,　the　performance　attenuation　is　negligible　even　after　30　000　cycles　in　accelerated　durability　tests　(ADT).　In　H2/Air　PEMFC　testing,　the　Pt-Ce-N-C　exhibits　exceptional　performance　and　durability　with　a　peak　power　density　of　1.229　W　cm-2　-twofold　of　Pt/C-　and　retaining　87.9%　of　its　performance　(1.08　W　cm-2)　after　30　000　ADT　cycles.　Combined　theoretical　and　experimental　results　reveal　that　Ce-Nx　sites　primarily　function　as　an　adsorption　site　for　reactants　due　to　their　strong　affinity　for　oxygen,　while　PtCe　alloy　and　Pt-Nx　serve　as　active　centers　for　ORR.　This　synergistic　interaction　between　the　alloy　and　dual-site　design　significantly　enhances　catalytic　activity　and　durability.