Vast　progress　in　semiconductor　photocatalysis　has　been　witnessed,　while　the　earth-abundant　insulators　were　seldomly　explored.　In　this　work,　we　exploited　insulator　BaSO4　as　photocatalyst　by　constructing　a　novel　branch　of　insulator-semiconductor　heterostructure　with　the　narrow-gap　CuS.　The　finely　designed　BaSO4-CuS　heterostructure　achieved　a　tetracycline　(TC)　degradation　pseudo-first-order　kinetic　constant　of　1.4　×　10−2　min−1,　which　was　311,　21　and　18　times　higher　than　that　of　BaSO4,　CuS　and　their　physical　mixture,　respectively.　Density　functional　theory　(DFT)　calculations　unraveled　that　the　intense　Cu-O　covalent　interaction　created　a　specific　channel　for　interfacial　electrons　transfer　from　semiconductor　to　insulator.　The　elevated　redox　potential　of　CuS　is　vital　for　the　accumulation　of　·O2-　and　motivation　of　·OH,　thus　remarkedly　accelerating　TC　mineralization.　Furthermore,　the　degradation　pathway　and　intermediates　of　TC　were　thoroughly　studied　through　LC-MS.　The　current　work　provides　new　perspectives　to　harvest　visible-light-driven　insulator　photocatalysts　and　demonstrates　its　promising　applications　for　environmental　remediation.　©　2022　Elsevier　B.V.