The　dynamic　evolution　of　active　site　coordination　structure　during　a　high-temperature　reaction　is　critically　significant　but　often　difficult　for　the　research　of　efficient　single-atom　catalysts　(SACs).　Herein,　we　for　the　first　time　report　the　in　situ　activation　behaviors　of　the　local　coordination　structure　of　Pt　single　atoms　(Pt-1)　during　the　high-temperature　oxidation　of　light　alkanes.　The　distinctly　enhanced　activity　of　the　catalyst　is　attributed　to　the　in　situ　evolved　Pt-1-oxygen　vacancy　(Pt-1-OV)　combination　ensemble　as　an　efficient　and　stable　active　site.　Theoretical　calculations　reveal　that　the　lattice　oxygen　adjacent　to　Pt-1　and　the　H　dissociated　from　CH4　constitute　the　lattice　hydroxyl,　which　is　the　initial　step　in　the　formation　of　the　Pt-1-OV　combination.　Pt-1　and　nearby　unsaturated　Mn　can　donate　the　charge　back　to　O-O　to　promote　the　dissociation　of　O-2.　This　work　provides　molecular-level　insight　into　the　in　situ　reaction-induced　evolution　of　a　single-atom　coordination　environment　for　designing　efficient　SACs　under　harsh　conditions.