In　this　study,　a　fluorescence　biosensor　based　on　the　peroxidase　mimicking　activity　of　platinum　nanoparticles　(Pt　NPs)　was　fabricated　for　rapid　detection　of　hypoxanthine　(Hx),　which　is　a　sensitive　indicator　of　the　freshness　of　aquatic　products.　The　fluorescence　intensity　of　the　sensing　system　had　a　linear　relationship　with　the　concentration　of　Hx　in　the　range　of　8-2500　mu　M,　and　the　limit　of　detection　was　as　low　as　2.88　mu　M　(S/N　=　3).　Moreover,　benefiting　from　the　excellent　selectivity　of　the　biosensor,　Hx　content　in　fish,　shrimp　and　squid　samples　could　be　quickly　detected　with　good　recovery　rates　(103.94-109.00%).　And　the　Pt　NPs　used　in　the　biosensor　was　reusable,　which　was　proved　by　the　recovery　rate　was　only　slightly　decreased　to　91%　after　three　cycles.　In　addition　to　the　advantages　of　facile　preparation　and　low　cost,　the　proposed　biosensor　will　be　a　promising　candidate　for　rapid　and　convenient　freshness　evaluation　of　aquatic　products.