Development　of　various　strategies　for　controllable　fabrication　of　core-shell　nanocomposites　(CSNs)　with　highly　active　photocatalytic　performance　has　been　attracting　ever-increasing　research　attention.　In　particular,　control　of　the　ultrathin　layer　TiO2　shell　in　constructing　CSNs　in　an　aqueous　phase　is　a　significant　but　technologically　challenging　issue.　Here,　this　paper　demonstrates　the　interface　assembly　synthesis　of　CdS　nanospheres@TiO2　core　shell　photocatalyst　via　the　electrostatic　interaction　of　negatively　charged　water-stable　titania　precursor　with　positively　charged　CdS　nanospheres　(CdS　NSPs),　followed　by　the　formation　of　the　ultrathin-layer　TiO2　shell　through　a　facile　refluxing　process　in　aqueous　phase.　The　as-formed　CdS　NSPs@TiO2　core　shell　nanohybrid　exhibits　a　high　visible-light-driven　photoactivity　for　selective　transformation　and　reduction　of　heavy　metal　ions.　The　ultrathin　TiO2　layer　coated　on　CdS　NSPs　results　in　excellent　light　transmission　property,　enhanced　adsorption　capacity,　and　improved　transfer　of　charge　carriers　and　lifespan　of　photoinduced　electron　hole　pairs,　which　would　prominently　contribute　to　the　significant　photoactivity　enhancement.　It　is　anticipated　that　this　facile　aqueous-phase　synthesis　strategy　could　be　extended　to　design　a　variety　of　more　efficient　CSN　photocatalysts　with　controllable　morphology　toward　target　applications　in　diverse　photoredox　processes.