Electrosynthesis　of　hydrogen　peroxide　(H2O2)　by　two-electron　oxygen　reduction　on　the　cathode　is　an　attractive　green　approach　for　environmental　remediation　and　chemical　industries.　In　this　study,　an　active　carbon　fiber　(ACF)　electrode　modified　with　graphite　carbon　nitride　(g-C3N4)　and　carbon　nanotubes　(CNTs)　is　fabricated　by　a　wet　ultrasonic　impregnation-calcination　method.　The　doping　content　of　g-C3N4,　CNTs　and　polytetrafluoroethylene　(PTFE)　is　optimized　by　response　surface　methodology　(RSM).　With　optimum　doping　content,　the　H2O2　generation　by　modified　ACF　increased　several　times,　indicating　the　physicochemical　and　electronic　transformation　of　ACF.　The　introduction　of　g-C3N4　modulates　the　electronic　structure　of　ACF,　alleviating　the　adsorption　energy　of　oxygen　and　coordinating　the　*　OOH　binding　capability.　Besides　reducing　the　oxygen　adsorption　energy,　CNTs　simultaneously　improve　the　conductivity　of　electrodes.　In　addition,　the　addition　of　an　appropriate　amount　of　PTFE　constructs　a　gas-liquid-solid　three-phase　equilibrium,　facilitating　oxygen　diffusion.　The　effects　of　operating　parameters　on　H2O2　generation　are　also　investigated　and　the　optimal　performance　is　achieved　at　current　=　0.2　A,　pH　=　3,　and　aeration　rate　=　0.32　L/min.　The　modified　ACF　shows　great　potential　in　the　practical　applications　for　in-situ　H2O2　electro-generation.&　nbsp;