In　this　work,　we　proposed　a　straightforward　self-assembly　and　in-situ　deposition　protocol　to　construct　Cu2O/g-C3N4/Ag　composites,　which　demonstrated　peroxidase-like　attribute　and　exceptional　SERS　activity.　These　composites　proved　to　be　an　effective　SERS　analysis　tool　for　detecting　organic　fungicides　like　malachite　green　(MG)　and　crystal　violet　(CV).　Remarkably,　they　achieved　detection　limits　as　low　as　10−9　M　in　DI　water　as　well　as　fish　pond　water,　and　exhibited　a　strong　linear　correlation　between　logarithmic　concentrations　and　SERS　intensities　(R2　≥　0.97).　Beyond　that,　with　the　aid　of　hydrogen　peroxide　(H2O2),　the　peroxidase-like　Cu2O/g-C3N4/Ag　composites　rapidly　degraded　MG　and　CV　molecules　within　just　5　min.　Furthermore,　their　practical　reusability　based　on　the　peroxidase-like　reaction　was　proved　by　high　SERS　performance　across　5　detection　cycles.　These　results　emphasize　the　immense　potential　of　Cu2O/g-C3N4/Ag　in　SERS-based　trace　fungicide　detection　and　suggest　future　applications　in　ecological　restoration　through　peroxidase-like　reactions.　©　2024　Elsevier　B.V.