By　means　of　density　functional　theory　(DFT)　computations,　we　investigated　the　electronic　and　optical　properties　of　B,F-monodoped　and　B/F-codoped　graphitic　carbon　nitride　(g-C3N4)　to　explore　the　doping　effects　on　the　photocatalytic　performance　of　g-C3N4.　It　is　found　that　F　atom　addition　plays　a　key　role　in　stabilizing　the　surface　of　g-C3N4　and　facilitating　B　atom　substitution　into　g-C3N4.　Among　the　different　doping　strategies,　only　B/F-codoping　does　not　have　localized　states　in　the　midgap,　which　act　as　recombination　centers　for　the　photogenerated　electron-hole　pairs.　All　the　doping　strategies　in　this　study　can　improve　the　utilization　ratio　of　visible　light　for　the　g-C3N4　photocatalyst.　Considering　the　relationship　of　overpotential　of　water　redox　reaction　over　g-C3N4　and　band　edge　positions　with　respect　to　the　water　redox　potentials,　only　the　F-doped　and　B/F-codoped　g-C3N4　satisfy　the　criterion　for　overall　water　splitting.　In　other　words,　the　B/F-codoping　strategy　not　only　meets　the　demands　of　no　recombination　centers　and　enhances　the　visible　light　utilization　ratio,　but　also　satisfies　the　need　of　overpotential.　Thus,　B/F-codoped　g-C3N4　is　expected　to　be　a　promising　photocatalyst　for　overall　water　splitting　under　visible　light.