Hydrogen　sulfide　(H2S),　as　a　hazardous　gas,　is　often　found　around　dump　areas.　Long　term　exposure　can　cause　harm　to　health,　it　is　highly　necessary　to　develop　some　simple　and　sensitive　methods　for　on-site　H2S　detection.　Herein,　a　convenient　photothermal　assay　has　been　designed　for　the　quantitation　of　H2S　using　a　handheld　thermometer　as　readout.　Au@Ag　nanocubes　(Au@Ag　NCs),　a　core-shell　nanocomposite　with　strong　light　absorption　at　∼450　nm,　was　chosen　as　a　novel　photothermal　agent　in　this　study.　Under　the　laser　irradiation　at　450　nm,　the　Au@Ag　NCs　show　a　strong　photothermal　effect,　and　a　significant　temperature　enhancement　can　be　measured　by　the　thermometer　easily.　The　presence　of　H2S　can　lead　to　the　deposition　of　sulfur　onto　Au@Ag　NCs,　altering　the　localized　surface　plasmon　resonance　absorption,　size,　surface　composition,　and　morphology　of　Au@Ag　NCs　and　hence　leading　to　the　reduction　of　photothermal　effect.　The　change　of　the　temperature　has　a　linear　relationship　with　the　H2S　concentration　in　the　range　of　0.5–80.0　μM　with　a　detection　limit　of　0.35　μM.　By　combining　with　simple　sample　purification　procedures,　the　developed　method　has　been　applied　to　detect　H2S　in　garbage　odor　gas　with　satisfactory　results.　©　2021　Elsevier　B.V.