Maleic　hydrazide　(MH)　is　a　commonly　used　plant　growth　regulator　and　herbicide.　However,　due　to　its　potential　mutagenicity,　carcinogenicity,　genotoxicity,　and　cytotoxicity,　sensitive　and　rapid　detection　of　MH　residues　in　foods　is　crucial.　Herein,　a　sensitive　and　reliable　surface-enhanced　Raman　scattering　(SERS)　sensor　for　MH　based　on　a　self-constructed　hydrogel　SERS　platform　is　proposed　for　the　first　time.　The　used　hydrogel　SERS　chips　contain　aggregated　Ag　nanoparticles　(a-AgNPs).　Under　the　irradiation　of　785　nm　laser,　the　a-AgNPs　provide　a　large　quantity　of　plasmonic　hots　to　produce　strong　electromagnetic　enhancement.　Thus,　strong　SERS　signal　of　MH　can　be　gained　on　the　hydrogel　SERS　platform.　In　addition,　the　unique　network　structure　of　hydrogel　greatly　improves　the　anti-interference　ability　to　the　complex　sample　matrix.　As　a　result,　the　developed　SERS　sensor　for　MH　shows　the　advantages　of　high　sensitivity　(a　low　detection　limit　of　50　ppb),　fast　response　(10　min),　and　high　selectivity.　The　reliability　of　the　sensor　is　supported　by　the　satisfactory　recoveries　of　92.80　-　105.6　%　in　actual　samples　(tea　and　potato).　The　constructed　SERS　sensor　provides　a　promising　approach　for　rapid　on-site　testing　of　MH　residues.