Schiff　base　reactions　are　widely　used　in　pharmacy,　catalysis,　and　volatile　aldehyde　detection.　However,　common　biomarker　sensing　methods　struggle　to　monitor　this　reaction　process　precisely　due　to　their　sensitivity,　their　time-consuming　nature,　and　complex　substrates.　Here,　we　introduce　the　Nanoparticle-on-Mirror　structure　for　in　situ　monitoring　this　reaction　process　through　the　application　of　a　Au　nanoparticle-p-Aminothiophenol-Au　thin-film　platform　by　surface-enhanced　Raman　scattering　(SERS).　Owing　to　the　exposure　of　-NH2　groups　and　the　local　ultra-strong　electromagnetic　field　in　the　nanocavity,　the　Schiff　base　reactions　process　can　be　rapidly　monitored　within　two　minutes.　Meanwhile,　the　monitoring　platform　can　detect　benzaldehyde　molecules　as　low　as　10-6　M,　showing　excellent　SERS　performance.　Notably,　the　Au-nanoparticle-p-Aminothiophenol-Au　thin-film　platform　exhibited　anti-interference　and　specificity,　being　able　to　identify　BA　in　the　presence　of　interference.　The　use　of　the　Au-nanoparticle-p-Aminothiophenol-Au　thin-film　platform　provides　a　sensing　method　for　Schiff　base　reactions　with　accuracy　and　simplicity　of　operation,　achieving　a　balanced　approach　for　low-cost　and　high-performance　real-time　monitoring,　which　is　expected　to　be　applied　in　various　catalytic　reaction　process　monitoring　and　catalyst　design　processes.