The　instability　and　insolubility　of　perovskite　quantum　dots　in　aqueous　solution　prohibit　applications　in　polar　solvents.　As　a　highly　toxic　gas　pollutant　and　also　an　endogenous　gaseous　signaling　molecule　existing　in　a　variety　of　physiological　processes,　hydrogen　sulfide　(H2S),　with　high　selectivity　and　high　specificity,　detection　is　of　great　significance.　In　this　study,　a　simple　device　has　been　designed　to　separate　H2S　from　aqueous　solution　and　CsPbBr3　quantum　dots　(CsPbBr3　QDs)　have　been　used　as　the　detection　probe　to　develop　a　novel　fluorescent　sensor　for　rapid　H2S　detection.　The　addition　of　hydrogen　sulfide　to　the　phosphoric　acid　solution　results　in　the　escape　of　H2S　from　the　aqueous　sample　and　hence　it　passing　into　the　n-hexane　solution　containing　CsPbBr3　QDs,　resulting　in　the　quenching　of　the　fluorescence　of　CsPbBr3　QDs.　The　fluorescence　intensity　of　the　system　has　a　linear　relationship　with　the　concentration　of　H2S　in　the　range　of　0-100　μM　with　the　detection　limit　of　0.18　μM.　The　proposed　system　has　been　applied　to　detection　of　H2S　in　rat　brain　microdialysate　with　satisfying　results.　The　potential　mechanism　regarding　the　quenching　of　fluorescence　from　CsPbBr3　QDs　by　H2S　has　been　studied　as　well.　Copyright　©　2019　American　Chemical　Society.