Rational　construction　of　high-efficiency　photoelectrodes　with　optimized　carrier　migration　to　the　ideal　active　sites,　is　crucial　for　enhancing　solar　water　oxidation.　However,　complexity　in　precisely　modulating　interface　configuration　and　directional　charge　transfer　pathways　retards　the　design　of　robust　and　stable　artificial　photosystems.　Herein,　a　straightforward　yet　effective　strategy　is　developed　for　compact　encapsulation　of　metal　oxides　(MOs)　with　an　ultrathin　non-conjugated　polymer　layer　to　modulate　interfacial　charge　migration　and　separation.　By　periodically　coating　highly　ordered　TiO2　nanoarrays　with　oppositely　charged　polyelectrolyte　of　poly(dimethyl　diallyl　ammonium　chloride)　(PDDA),　MOs/polymer　composite　photoanodes　are　readily　fabricated　under　ambient　conditions.　It　is　verified　that　electrons　photogenerated　from　the　MOs　substrate　can　be　efficiently　extracted　by　the　ultrathin　solid　insulating　PDDA　layer,　significantly　boosting　the　carrier　transport　kinetics　and　enhancing　charge　separation　of　MOs,　and　thus　triggering　a　remarkable　enhancement　in　the　solar　water　oxidation　performance.　The　origins　of　the　unexpected　electron-withdrawing　capability　of　such　non-conjugated　insulating　polymer　are　unambiguously　uncovered,　and　the　scenario　occurring　at　the　interface　of　hybrid　photoelectrodes　is　elucidated.　The　work　would　reinforce　the　fundamental　understanding　on　the　origins　of　generic　charge　transport　capability　of　insulating　polymer　and　benefit　potential　wide-spread　utilization　of　insulating　polymers　as　co-catalysts　for　solar　energy　conversion.　Uniform　non-conjugated　insulating　polymer　encapsulation　on　the　metal　oxides　remarkably　enhances　the　spatially　directional　electron　transport,　wherein　the　ultrathin　insulating　polymer　functions　as　an　electron　trap　to　facilitate　the　charge　separation　in　solar　water　splitting.　image