Quantum　dots　are　a　promising　star　material　in　the　field　of　new　optoelectronic　devices　due　to　their　excellent　optical　and　electrical　properties.　In　this　work,　we　prepare　the　CdSe/CdS@PDMS-PUa　composite　by　encapsulating　core/shell　CdSe/CdS　quantum　dots　into　an　amino-terminated　polydimethylsiloxane(PDMS-PUa)　polymer　matrix,　which　shows　water-driven　enhanced　photoluminescence(PL)　intensity　and　photoluminescence　quantum　yield(PLQY).　After　the　analysis　of　fluorescent　decay　curve　and　diffuse　reflectance　spectrum,　the　reason　for　this　enhancement　is　found　to　be　the　passivation　of　the　surface　defects　of　the　quantum　dots　by　H3O+　and　OH-　in　water,　making　the　unit　cell　of　the　quantum　dots　more　idealized.　However,　when　the　composite　is　taken　out　of　the　water　for　drying,　the　defect　states　are　exposed　again,　and　both　PL　and　PLQY　return　to　their　original　values.　Inspired　by　the　water-driven　PL　reversibility　in　CdSe/CdS@PDMS-PUa　composite,　a　liquid　height　sensor　with　fluorescence　response　is　proposed　based　on　the　CdSe/CdS@PDMS-PUa　composite,　which　can　judge　the　liquid　height　value　in　the　container　through　the　change　of　fluorescence　intensity.　These　findings　not　only　reveal　the　reversible　characteristics　of　CdSe/CdS　quantum　dots,　but　also　broaden　the　application　of　quantum　dots　polymer　composites　in　the　field　of　optoelectronics,　which　has　important　scientific　significance　and　application　prospects.　©　2022,　Science　Press.　All　right　reserved.