Disclosed in the present invention are a tungsten oxide nanorod/tin ion modified titanium carbide quantum dot/indium sulfide nanosheet composite material and a preparation method therefor. In the present invention, tin ions are introduced into the composite material, so that the efficiency of photocatalytic reduction of hexavalent chromium in water and decomposition of water to produce hydrogen can be improved. Compared with the tungsten trioxide/titanium carbide quantum dot/indium sulfide composite material introduced with titanium carbide quantum dots which are not modified by tin ions, the Z-type heterojunction composite material constructed by means of the present invention can significantly improve the photocatalytic efficiency. Experiments prove that the performance of the tungsten trioxide/tin ion modified titanium carbide quantum dot/indium sulfide composite material for respectively rapidly reducing hexavalent chromium in water and decomposing water to produce hydrogen under visible light is significantly better than that of tungsten trioxide/titanium carbide quantum dot/indium sulfide. After 6 minutes of irradiation under visible light, hexavalent chromium is completely reduced and removed from water where the Z-type heterojunction of tungsten oxide nanorod/tin ion modified titanium carbide quantum dot/indium sulfide nanosheet is located.