Photocatalysis　is　a　green　technology　which　could　sustainably　convert　CO2　into　value-added　chemicals　by　using　solar　energy.　Under　xenon　light　irradiation,　Mn2O3/MgTi2O5　nanocomposites　synthesized　by　two-step　hydrothermal　method　greatly　increase　photocatalytic　activity　of　CO2　reduction.　The　optimal　yield　420.53　mu　mol　g-　1　h-　1　for　CH4　is　achieved　at　a　ratio　1:10　(W/W)　of　Mn2O3　to　MgTi2O5,　with　selectivity　of　98.1　%,　i.e.,　4　and　33　times　larger　than　those　of　individual　MgTi2O5　and　Mn2O3,　respectively.　The　superior　photocatalytic　performance　is　attributed　to　the　formation　of　S-type　heterojunction,　valence　change　of　Mn3+/Mn4+,　and　the　bridging　effect　of　Mg　migration,　which　facilitates　the　separation　and　transfer　of　photogenerated　electrons　and　holes.　Mn2O3/　MgTi2O5　constructs　an　efficient　redox　photocatalytic　system　composed　of　a　light　trapping　component　(Mn2O3),　electron　transport　channel　(Mg　penetrating　Mn2O3),　mutually　separated　reduction　center　(MgTi2O5)　and　oxidation　center　(Mn2O3).　The　potential　Mn2O3/MgTi2O5　photocatalyst　for　CO2　reduction　provides　new　insights　to　design　novel　efficient　photocatalyst　composites　akin　to　biological　photosynthesis.