Fish　product　is　one　of　the　main　seafood　with　the　disadvantage　of　easy　to　perish.　Various　indexes　and　diverse　methods　have　been　developed　to　evaluate　the　fish　freshness,　but　most　of　them　are　complex　and　cannot　be　applied　for　on-field　detection.　In　this　study,　we　reported　a　simple,　visual　and　economical　multicolor　biosensor　based　on　the　etching　of　gold　nanorods　(GNRs)　to　evaluate　the　fish　freshness　with　the　naked　eye.　Hypoxanthine　(Hx)　is　chosen　as　the　index　of　fish　freshness　and　it　react　with　the　dissolved　oxygen　to　produce　H2O2　at　the　presence　of　xanthine　oxidase　(XOD).　Then　GNRs　are　etched　quickly　by　the　H2O2　in　the　presence　of　Fe2+　Correspondingly,　the　GNRs　surface　plasmon　resonance　(SPR)　is　regulated　and　results　in　a　distinctly　color　change　of　the　system,　which　can　be　easily　distinguished　with　the　naked　eye.　Therefore,　the　concentration　of　Hx　in　the　fish　samples　can　be　semi-quantitatively　analyzed　with　the　naked　eye.　The　proposed　multicolor　Hx　sensor　has　been　successfully　applied　to　the　detection　of　Hx　in　fish　samples.　(C)　2017　Elsevier　B.V.　All　rights　reserved.