The　semiconductor-insulator　heterostructure,　characterized　by　outstanding　economic-efficiency　and　catalytic　activity,　represents　a　promising　photocatalyst　for　practical　pollutants　degradation.　However,　achieving　energy　band　matching　between　semiconductors　and　insulators　remains　a　challenge.　In　this　study,　we　meticulously　designed　and　synthesized　a　band-matched　semiconductor-insulator　photocatalysts　(AgI-BaCO3),　leveraging　the　in-situ　nucleation　of　ultrafine　AgI　nanoparticles　on　BaCO3　surface.　The　finely　crafted　heterostructure　notably　enhanced　degradation　efficiency　of　tetracycline　over　both　pure　AgI　and　BaCO3,　demonstrating　a　remarkable　pseudo-first-order　kinetic　rate　constant　that　surpassed　them　by　27.2　and　33.5　times,　respectively.　The　density　functional　theory　calculations　uncovered　that　the　intense　covalent　interaction　between　AgI　and　BaCO3　established　a　specific　channel　for　interfacial　charge　carriers.　The　generated　CO3　center　dot-　radicals　as　the　main　active　species　markedly　expedited　the　removal　of　antibiotics.　Furthermore,　the　catalysts　demonstrated　robust　activity　in　real　wastewater　and　surface　water.　This　work　supplies　a　novel　reference　for　constructing　insulator-based　photocatalysts　and　elucidates　its　potential　application　in　actual　aquatic　environments.