Halide　perovskites　and　derivatives　have　been　used　as　emerging　photocatalysts　due　to　their　unique　optoelectronic　and　structural　diversity.　However,　compared　with　the　well-explored　photophysical　processes　for　light-driven　more　energetic　carriers　to　trigger　redox　reactions,　catalytic　effects　on　the　surface　of　halide　perovskite　or　their　derivatives　for　chemical　transformations　between　reactive　species　are　seldom　addressed,　which　is　equally　important　for　improving　the　efficiency　for　halide　perovskite-based　photocatalysts.　Here,　we　demonstrate　that　Cs3Bi2Br9　sites　in　the　Cs3Bi2Br9/CdS　heterojunction,　not　only　participate　in　light-driven　processes,　but　also　play　a　vital　role　for　the　activation　and　conversion　of　key　intermediates　during　C(sp3)-H　bond　transformation,　via　a　more　thermodynamically　and　kinetically　favorable　surface　reaction　pathway.　Besides,　various　aromatic　hydrocarbons　can　be　effectively　photocatalytic　converted　to　corresponding　aldehydes/ketones　as　major　products.　This　work　highlights　the　importance　of　surface　catalysis　mechanism　in　photocatalysis　not　only　for　halide　perovskites　but　also　for　other　semiconductors.