Precisely　controlling　the　strain　of　Pt-based　intermetallic　to　ensure　high　performance　and　stability　is　a　massive　task　for　sustainable　proton-exchange-membrane-fuel-cells.　Herein,　the　Al　single-atom　was　trapped　into　the　L12-Pt3Co　intermetallic　core　to　precisely　tailor　the　strain　state　on　the　Pt-skin　for　fast　oxygen　reduction　reaction　kinetics.　Theoretical　calculations　firstly　predicted　that　only　tailored　tension　can　accelerate　the　protonation　of　O2　on　L12-Pt3Co@Pt　without　creating　an　additional　energy　barrier　for　subsequent　oxygen-containing　intermediates　desorption.　Experimentally,　Al　single-atom　confined　in　the　L12-Pt3Co　lattice　by　substituting　partial　Co　occupancy,　imposing　tailored　∼　0.2　%　tension　on　Pt-skin　compared　to　the　L12-Pt3Co.　L12-Al-Pt3Co@Pt/C　exhibits　enhanced　mass　activity　which　is　ten-time　improvement　over　commercial　Pt/C.　More　significantly,　XAS　and　DFT　results　reveal　that　the　Al　single-atom　can　strengthen　the　Pt-Co　bonding,　enhancing　the　stability　of　L12-Al-Pt3Co@Pt/C　in　oxygen　reduction.　This　work　provides　an　avenue　to　design　the　strain　by　single-atom　for　sustainable　energy　conversion　technologies.　©　2024　Elsevier　B.V.