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　＜4 nm),　but　also　efficiently　stabilizes　intermetallic　nanoparticles and　sufficient　exposure　of　active　sites　during　the　ORR　process.　The　optimized　catalyst　(L12‐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.