Modulating　the　crystal　structure　of　the　semiconductor　photocatalyst　is　important　to　separate　and　migrate　the　photogenerated　electrons　and　holes　for　good　photocatalytic　performance.　Here,　we　show　that　Sn　replaces　part　of　In　atoms　in　In2S3　nanosheets　to　form　bimetallic　sulfide　In4SnS8,　which　induces　the　distortion　of　the　[InS6]　octahedron　and　improves　the　crystal　symmetry　of　the　spatial　arrangement　of　[SnS6]　and　[InS6]　octahedrons.　The　twisted　[InS6]　octahedron　can　promote　the　separation　of　photogenerated　carriers.　The　improved　symmetry　of　the　crystal　structure　promotes　the　migration　of　separated　electrons　through　reducing　the　lattice　scattering　effect　of　the　crystal　structure,　which　is　favorable　to　the　rapid　transfer　of　electrons　from　the　bulk　to　the　surface.　Both　endow　In4SnS8　with　generation　rates　of　CH4　and　CO　about　20　and　12　times　higher　than　those　of　In2S3　and　SnS2　for　the　catalytic　CO2　photoreduction　reaction,　respectively.　This　work　offers　basic　guidance　to　rationally　design　a　photocatalyst　for　the　improved　separation　of　photoinduced　electron/hole　pairs.