Quantum　dots　(QDs)　colloidal　nanocrystals　are　attracting　enduring　interest　by　scientific　communities　for　solar　energy　conversion　due　to　generic　physicochemical　merits　including　substantial　light　absorption　coefficient,　quantum　confinement　effect,　enriched　catalytically　active　sites,　and　tunable　electronic　structure.　However,　photo-induced　charge　carriers　of　QDs　suffer　from　ultra-short　charge　lifespan　and　poor　stability,　rendering　controllable　vectorial　charge　modulation　and　customizing　robust　and　stable　QDs　artificial　photosystems　challenging.　Herein,　tailor-made　oppositely　charged　transition　metal　chalcogenides　quantum　dots　(TMCs　QDs)　and　MXene　quantum　dots　(MQDs)　are　judiciously　harnessed　as　the　building　blocks　for　electrostatic　layer-by-layer　assembly　buildup　on　the　metal　oxides　(MOs)　framework.　In　these　exquisitely　designed　LbL　assembles　MOs/(TMCs　QDs/MQDs)n　heterostructured　photoanodes,　TMCs　QDs　layer　acts　as　light-harvesting　antennas,　and　MQDs　layer　serves　as　electron-capturing　mediator　to　relay　cascade　electrons　from　TMCs　QDs　to　the　MOs　substrate,　thereby　yielding　the　spatially　ordered　tandem　charge　transport　chain　and　contributing　to　the　significantly　boosted　charge　separation　over　TMCs　QDs　and　solar　water　oxidation　efficiency　of　MOs/(TMCs　QDs/MQDs)n　photoanodes.　The　relationship　between　interface　configuration　and　charge　transfer　characteristics　is　unambiguously　unlocked,　by　which　photoelectrochemical　mechanism　is　elucidated.　This　work　would　provide　inspiring　ideas　for　precisely　mediating　interfacial　charge　transfer　pathways　over　QDs　toward　solar　energy　conversion.　Cascade　charge　transfer　channel　is　elaborately　designed　over　transition　metal　chalcogenides　quantum　dots　via　a　facile　layer-by-layer　assembly　strategy　for　significantly　boosted　solar　water　oxidation.　image