The　morphology　and　structure　of　photocatalyst　play　an　important　role　in　photocatalytic　activity.　SiC　semiconductor　is　considered　as　a　promising　material　for　the　photocatalytic　CO2　reduction　due　to　its　negative　conduction　band　position.　Herein,　SiC　nanocages　is　creatively　synthesized　by　simple　low-temperature　molten-salt-mediated　magnesiothermic　reduction　method　with　using　SiO2　as　template.　The　morphology　and　phase　composition　of　SiC　nanocages　can　be　controlled　by　magnesium　dosage　and　reaction　temperature.　The　2H　and　3C　crystal　phase　in　SiC　nanocage　can　form　heterophase　junctions　uniformly　to　effectively　accelerate　the　photogenerated　electron　transfer,　and　plays　a　key　role　in　improving　the　photocatalytic　activity　of　2H/3C-SiC　samples.　The　optimal　SiC　nanocage　sample　possesses　a　CO　generation　rate　of　4.68　μmol　g-1h−1　for　photocatalytic　CO2　reduction,　which　is　3.25　times　higher　than　that　of　commercial　SiC.　©　2022　Elsevier　Inc.