Monolayer　HNb3O8　nanosheets,　as　a　platform,　were　prepared　for　investigating　the　mechanism　of　photosensitized　degradation　of　RhB.　We　found　that　RhB　molecules　were　capable　to　absorb　on　HNb3O8　nanosheets　via　a　strong　interaction　between　the　-N(Et)(2)　group　in　RhB　molecules　and　surface　Lewis　acid　sites　on　HNb3O8　nanosheets,　contribution　to　an　easier　oxidation　of　RhB　molecules.　Thanks　to　the　suitable　conduction　band　of　HNb3O8　nanosheets,　electrons　transferred　from　excited　RhB　to　HNb3O8　nanosheets　effectively　and　reduced　the　dissolved　O-2　in　the　reaction　solution　into　O-2(-center　dot)　immediately,　resulting　in　the　efficient　photosensitized　degradation　of　RhB.