Nanozymes　are　ideal　materials　for　designing　colorimetric　sensors,　and　the　spontaneous　catalytic　effect　in　most　of　nanozymes　commonly　leads　to　instability　of　the　colorimetric　signal.　To　improve　this　limitation,　photoresponsive　nanozymes　as　a　switch　under　specific-light　irradiation　are　used　to　regulate　the　reaction　process　in　a　controlled　manner.　Strontium　titanate　(SrTiO3)　is　a　high-performance　photocatalyst,　whose　heterojunctions　formed　with　reduced　graphene　oxide　(rGO)　are　promising　to　efficiently　induce　the　separation　of　carriers,　further　generating　abundant　radicals　to　colorize　the　substrate.　Here,　the　SrTiO3-rGO　composites　with　a　high　specific　surface　area　were　synthesized　by　hydrothermal　method　and　showed　excellent　peroxidase-like　activity　under　ultraviolet　irradiation.　The　affinity　for　3,3′,5,5′-tetramethylbenzidine　is　equivalent　to　19　times　that　of　horseradish　peroxidase　and　the　reaction　mechanism　is　analyzed　based　on　reactive　intermediates(·O2-)　and　elemental　valence　changes.　A　colorimetric　sensor　based　on　SrTiO3-rGO　with　high　sensitivity,　low　limit　(56　nM),　and　wide　linear　range　(1–100　µM)　is　constructed　for　detecting　tannins　in　tea　samples.　This　visualization　model　provides　a　reliable　idea　for　the　quantitative　analysis　of　trace　substances.　©　2023　Elsevier　B.V.