Construction　of　S-scheme　heterojunction　for　photocatalytic　conversion　of　CO2　into　carbon-neutral　fuels　under　sunlight　is　of　paramount　value　for　the　sustainable　development　of　energy.　However,　few　reports　are　concerned　the　local　structure　and　electronic　structure　of　semiconductor　heterojunction,　which　are　importance　of　understanding　the　effect　of　heterojunction　structure　on　the　photocatalytic　property.　In　this　work,　hierarchical　alpha-Fe2O3/　g-C3N4　S-scheme　heterojunctions　were　manufactured　via　an　in　situ　self-assembly　strategy　for　the　efficient　reduction　of　CO2.　The　generation　rate　of　main　product　CO　for　optimal　alpha-Fe2O3/g-C3N4　heterojunction　is　up　to　215.8　mu　mol　g-1　h-1,　with　selectivity　of　93.3　%,　which　is　17.5　and　6.1　times　higher　than　those　of　pristine　Fe2O3　and　g-C3N4,　respectively.　The　local　structure　and　electronic　structure　for　alpha-Fe2O3/g-C3N4　heterojunction　are　probed　by　hard　X-Ray　Absorption　Fine　Structure　(XAFS)　and　soft　X-Ray　Absorption　Spectroscopy　(XAS),　as　well　as　density-functional　theory　(DFT)　calculations.　It　is　found　that　the　Fe(d)-N(p)　bond　formed　in　alpha-Fe2O3/g-C3N4　heterojunction　precisely　connects　the　conduction　band　(CB)　of　Fe2O3　and　the　valence　band　(VB)　of　g-C3N4,　which　minimizes　the　charge　transfer　distance　and　facilitates　CO2　photoreduction　activity.　This　work　provides　important　information　for　understanding　the　influence　of　interface　local　and　electronic　structure　on　the　performance　of　photo-catalytic　reduction　of　CO2　at　the　atomic　level.