The　stoichiometric　photocatalytic　reaction　of　CO2　with　H2O　is　one　of　the　great　challenges　in　photocatalysis.　Here,　we　construct　a　Cu2O-Pt/SiC/IrOx　composite　by　a　controlled　photodeposition　and　then　an　artificial　photosynthetic　system　with　Nafion　membrane　as　diaphragm　separating　reduction　and　oxidation　half-reactions.　The　artificial　system　exhibits　excellent　photocatalytic　performance　for　CO2　reduction　to　HCOOH　and　H2O　oxidation　to　O-2　under　visible　light　irradiation.　The　yields　of　HCOOH　and　O-2　meet　almost　stoichiometric　ratio　and　are　as　high　as　896.7　and　440.7　mu　molg(-1)h(-1),　respectively.　The　high　efficiencies　of　CO2　reduction　and　H2O　oxidation　in　the　artificial　system　are　attributed　to　both　the　direct　Z-scheme　electronic　structure　of　Cu2O-Pt/SiC/IrOx　and　the　indirect　Z-scheme　spatially　separated　reduction　and　oxidation　units,　which　greatly　prolong　lifetime　of　photogenerated　electrons　and　holes　and　prevent　the　backward　reaction　of　products.　This　work　provides　an　effective　and　feasible　strategy　to　increase　the　efficiency　of　artificial　photosynthesis.