The　sluggish　kinetics　of　oxygen　reduction　reaction　(ORR)　and　unsatisfactory　durability　of　Pt-based　catalysts　are　severely　hindering　the　commercialization　of　proton-exchange-membrane　fuel　cells　(PEMFCs).　In　this　work,　the　lattice　compressive　strain　of　Pt-skins　imposed　by　Pt-based　intermetallic　cores　is　tailored　for　highly　effective　ORR　through　the　confinement　effect　of　the　activated　nitrogen-doped　porous　carbon　(a-NPC).　The　modulated　pores　of　a-NPC　not　only　promote　Pt-based　intermetallics　with　ultrasmall　size　(average　size　of　2-Pt3Co@ML-Pt/NPC10)　achieves　excellent　mass　activity　(1.72　A　mgPt−1)　and　specific　activity　(3.49 mA　cmPt−2),　which　are　11-　and　15-fold　that　of　commercial　Pt/C,　respectively.　Besides,　owing　to　the　confinement　effect　of　a-NPC　and　protection　of　Pt-skins,　L12-Pt3Co@ML-Pt/NPC10　retains　98.1%　mass　activity　after　30 000　cycles,　and　even　95%　for　100 000　cycles,　while　Pt/C　retains　only　51.2%　for　30 000　cycles.　Rationalized　by　density　functional　theory,　compared　with　other　metals　(Cr,　Mn,　Fe,　and　Zn),　L12-Pt3Co　closer　to　the　top　of　＇volcano＇　induces　a　more　suitable　compressive　strain　and　electronic　structure　on　Pt-skin,　leading　to　an　optimal　oxygen　adsorption　energy　and　a　remarkable　ORR　performance.　©　2023　Wiley-VCH　GmbH.