Cocatalysts　have　been　extensively　employed　to　improve　gas　sensing　performance　in　gas　detection.　However,　the　interface　effect　of　the　heterojunction　on　gas　sensing　has　rarely　been　addressed.　This　study　investigated　the　interface　effect　of　constructive　hierarchical　In2S3/In2O3　nanoflowers　on　NO2　gas　sensitivity　using　a　rapid　and　facile　microwave-assisted　hydrothermal　method.　The　structure　was　then　modulated　from　In2S3,　to　In2S3/In2O3　heterostructures,　and　finally　In2O3　alone　by　increasing　the　calcination　time.　In2S3/In2O3　heterostructures　with　an　appropriate　interface　were　found　to　significantly　promote　NO2　gas　sensitivity　with　a　high　gas-sensing　selectivity　compared　with　pure　In2S3　and　In2O3.　An　interface　enhancement　model　has　also　been　developed.　The　strong　interfacial　coupling　effect　was　key　to　high　gas　sensitivity,　which　likely　originated　from　hole-electron　pair　separation　through　tuning　of　the　interfacial　electronic　structure　of　In2S3/In2O3　nanoflowers　using　different　calcination　times.　This　resulted　in　improved　charge　separation　efficiency　and　carrier　collection　efficiency　of　electrons　from　In2S3　to　In2O3,　and　increased　active　sites.　This　boosted　gas　diffusion　and　adsorption,　accelerated　surface　chemical　reactions,　and　expedited　charge　transport　and　kinetic　processes.　This　work　provides　a　new　approach　for　designing　high-performance　sensor　using　the　interface　effect　of　heterostructure　nanomaterials.