The　composition　and　evolution　of　interfacial　species　play　a　key　role　during　electrocatalytic　process.　Unveiling　the　structural　evolution　and　intermediate　during　catalytic　process　by　in　situ　characterization　can　shed　new　light　on　the　electrocatalytic　reaction　mechanism　and　develop　highly　efficient　catalyst.　However,　directly　probing　the　interfacial　species　is　extremely　difficult　for　most　spectroscopic　techniques　due　to　complicated　interfacial　environment　and　ultra-low　surface　concentration.　Herein,　electrochemical　core-shell　nanoparticle　enhanced　Raman　spectroscopy　is　utilized　to　probe　the　composition　and　evolution　processes　of　interfacial　species　on　Au@Pt,　Au@Co,　and　Au@PtCo　core—shell　nanoparticle　surfaces.　The　spectral　evidences　of　interfacial　intermediates　including　hydroxide　radical　(OH*),　superoxide　ion　(O2−),　as　well　as　metal　oxide　species　are　directly　captured　by　in　situ　Raman　spectroscopy,　which　are　further　confirmed　by　the　both　isotopic　experiment　and　density　functional　theory　calculation.　These　results　provide　a　mechanistic　guideline　for　the　rational　design　of　highly　efficient　electrocatalysts.　©　Tsinghua　University　Press　2023.