Conjugated　polymers　(CPs)　have　garnered　increasing　attention　in　the　field　of　photocatalysis　due　to　their　stability　and　molecular　tunability.　Understanding　the　structure-property　relationship　in　CPs　and　addressing　appropriate　molecular　design　strategies　are　pivotal　to　improving　the　photocatalytic　performance　of　CPs.　Herein,　a　new　efficient　cyano　(CN)　engineering　approach　was　proposed　to　promote　the　photocatalytic　performance　of　CPs,　and　three　representative　CP-based　photocatalysts　with　different　CN　contents　were　tailor-made　to　investigate　the　relationship　between　CN　functionalization　and　photocatalytic　activity.　A　series　of　systematically　experimental　and　theoretical　studies　reveal　that　CN　functionalization　contributes　to　strengthening　the　donor-acceptor　(D-A)　interaction,　enhancing　the　light　absorption　ability,　charge　separation/transfer　efficiency,　and　hydrophilicity　of　CPs,　and　also　facilitating　the　output　of　separated　photoinduced　electrons　from　CPs　to　Pt　cocatalyst.　Thus,　the　dicyano-functionalized　polymer　(P-2CN)　manifests　an　attractive　photocatalytic　performance　in　hydrogen　production.　This　study　provides　a　facile　strategy　to　develop　excellent　CP-based　photocatalysts　for　solar　fuel　production.