The　tunable　structures　and　versatile　properties　for　conjugated　polymers　(CPs)　make　them　viable　as　a　molecular　platform　for　photocatalytic　water　splitting.　Normally,　structure　design　of　polymer　photocatalyst　is　focus　on　tuning　its　optical　band　structure　or　charge-separation　ability,　the　importance　of　electron-output　ability　in　photocatalytic　process　is　always　ignored.　This　study　demonstrates　a　molecular　engineering　strategy　by　introducing　an　electron-output　＇tentacle＇　site,　i.e.　dibenzothiophene-S,S-dioxide　(FSO)　unit,　into　the　polymer　backbone　to　construct　a　series　of　donor-acceptor　type　conjugated　polymer　photocatalysts　for　efficient　hydrogen　evolution,　which　not　only　results　in　optimized　light　absorption　ability　and　excellent　exciton-separation,　but　also　leads　to　the　efficient　electron-output　ability.　Detailed　DFT　calculations　further　theoretically　confirm　the　vital　role　of　FSO　unit　as　an　electron-output　＇tentacle＇　site.　©　2019