All-inorganic　perovskite　quantum　dots　(CsPbX3　QDs)　with　bright　photoluminescence　are　suitable　for　application　in　optoelectronic　field,　but　their　extreme　instability　and　insolubility　in　aqueous　solution　limit　their　development　in　other　fields.　Herein,　for　the　first　time,　we　encapsulated　CsPbBr3　QDs　using　sulfobutylether-beta-cyclodextrins　to　form　nanocomposite　(CsPbBr3　@SBE-beta-CD　nanocomposite)　with　high　water　solubility　and　stability　via　a　hostguest　interaction　strategy,　in　which　the　PL　intensity　remained　above　100%　of　the　initial　value　after　3　h　storage　in　water.　Hydrogen　sulfide　(H2S)　is　known　to　be　an　important　mediator　of　diverse　cellular　functions　in　health　and　in　disease,　which　is　important　to　develop　a　selective　and　portable　detection　method　for　H2S.　The　obtained　CsPbBr3　@SBE-beta-CD　nanocomposite　was　employed　to　develop　a　photothermal　sensor　for　quantitative　detection　of　H2S　using　a　thermometer　as　signal　readout.　Specifically,　the　obtained　CsPbBr3　@SBE-beta-CD　nanocomposite　was　used　as　the　photothermal　probe　while　H2S　acted　as　a　switch　of　the　photothermal　probe,　and　the　photothermal　sensor　was　triggered　by　the　reaction　between　H2S　and　CsPbBr3　@SBE-beta-CD　nanocomposite.　Notably,　the　naked　eye　and　fluorescence　spectrophotometer　could　also　be　the　signal　readout　for　this　strategy,　and　their　detection　range　and　limit　of　detection　were　not　better　than　those　of　the　proposed　photothermal　sensor.　On　the　basis　of　this　H2S-triggered　photothermal　sensor,　H2S　was　successfully　detected　at　a　concentration　as　low　as　5.0　mu　M　in　organs　of　adult　zebrafish　at　room　temperature　for　10　min.　Such　innovative　strategy　enables　new　opportunity　for　the　development　of　affordable　assays,　especially　as　point-of-care　testing　in　low-resource　settings.