Exquisite　modulation　of　spatial　charge　transfer　has　been　deemed　an　efficacious　strategy　to　boost　the　solar　conversion　efficiency.　Nevertheless,　tunable　control　over　directional　charge　transfer　in　photocatalysis　to　ideal　reaction　sites　still　constitutes　a　challenging　task.　In　this　work,　cadmium　sulfide　(CdS),　one　of　the　most　quintessential　transition　metal　sulfides,　was　used　to　demonstrate　how　to　progressively　construct　a　cascade　charge　transfer　channel　via　in　situ　phase　self-transformation　coupled　with　favorable　interface　engineering.　The　in　situ　phase　self-transformation　of　CdS　to　CdSe　on　the　surface　was　triggered　followed　by　electrostatic　self-assembly　of　MoS2　quantum　dots　(QDs)　on　the　CdS@CdSe　core-shell　nanostructure,　resulting　in　a　CdS@CdSe-MoS2　QD　ternary　heterostructure　with　well-defined　tailor-made　interfaces.　Significantly,　CdS@CdSe-MoS2　QDs　demonstrated　conspicuously　enhanced　photocatalytic　water　splitting　performance　in　comparison　with　their　single　and　binary　counterparts　under　visible　light　irradiation　along　with　favorable　photostability　and　substantial　apparent　quantum　yield.　This　is　predominantly　ascribed　to　the　generation　of　a　cascade　charge　transport　channel　in　the　ternary　heterostructure　arising　from　the　cooperativity　of　in　situ　CdSe　encapsulation　and　pinpoint　MoS2　QD　decoration.　More　importantly,　the　in　situ　formed　ultrathin　CdSe　interlayer　plays　a　crucial　role　in　mediating　the　charge　transfer　cascade,　affording　suitable　energy　level　alignment,　and　shielding　the　defect　sites　of　CdS　NWs,　thereby　markedly　retarding　charge　recombination　and　prolonging　the　lifetime　of　charge　carriers.　Furthermore,　self-assembled　MoS2　QDs　on　the　CdS@CdSe　core-shell　framework　further　contribute　to　the　directional　charge　flow　to　the　active　sites　for　hydrogen　production.