Charge　generation　and　separation　are　two　key　issues　in　developing　a　high-efficiency　semiconductor　for　the　visible-light-driven　photocatalysis.　Here,　we　use　the　layered　perovskite-type　wide-gap　semiconductor　La2Ti2O7　(LTO)　as　a　model　to　systematically　explore　the　synergistic　effect　of　doping　(with　sulfur　or　nitrogen)　and　heterojunction　(with　graphitic　C3N4)　on　improving　visible　light　absorption　and　photoexcited　charge　separation　by　means　of　density　functional　theory　calculations.　It　is　found　that　the　anion　(N　or　S)　doping　into　the　LTO(010)　surface　can　not　only　shift　the　optical　absorption　edge　to　the　visible　region,　but　also　creates　some　partially　occupied　or　unoccupied　states　in　the　band　gap　that　would　facilitate　the　formation　of　recombination　centers.　For　the　purpose　of　promoting　electron-hole　separation,　the　(N　or　S-doped)　LTO(010)　surfaces　were　hybridized　with　the　monolayer　g-C3N4.　Interestingly,　we　found　that　the　(S-doped)　LTO/g-C3N4　heterostructure　forms　a　type-II　heterojunction,　with　the　valence　band　maximum　residing　in　the　(S-doped)　LTO　and　the　conduction　band　minimum　in　g-C3N4,　respectively.　This　band　alignment　feature　facilitates　efficient　electron-hole　separation.　Moreover,　we　found　that　the　S-doped　LTO/g-C3N4　composite　has　a　short　interfacial　distance　(about　2.1　angstrom),　implying　that　the　interfacial　interaction　of　this　composite　might　be　a　chemical　bond　rather　than　a　weak　van　der　Walls　interaction.　The　chemical　bonding　can　enhance　charge　separation.　Our　theoretical　findings　provide　design　principles　for　optimizing　the　photocatalytic　performance　of　the　wide-gap　photocatalysts　and　demonstrate　that　the　S-doped　LTO/g-C3N4　composite　would　be　a　potential　candidate　for　the　photocatalysis　of　water　splitting.