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.