Mixed　metal　oxides　with　a　spinel　structure　have　exhibited　great　opportunities　for　photocatalytic　CO2　reduction;　however,　the　abilities　of　their　sulfide　counterparts　in　this　promising　area　are　much　less　reported.　Herein,　we　demonstrate　the　synthesis　of　a　ternary　metal　sulfide,　namely　NiCo2S4,　and　its　first　application　to　catalyze　the　CO2　photoreduction　reaction　under　visible　light　irradiation.　The　NiCo2S4　material　is　prepared　through　a　coupled　solvothermal-ion　exchange　strategy,　and　is　fully　checked　by　diverse　characterizations,　including　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　X-ray　photoelectron　spectroscopy　(XPS),　energy-dispersive　X-ray　spectroscopy　(EDX)　and　N-2　sorption　measurements.　Under　visible　light　irradiation　in　a　classic　tandem　photochemical　system,　this　non-noble-metal　NiCo2S4　catalyst　affords　a　considerable　activity　and　high　stability　for　CO2　deoxygenative　reduction,　delivering　a　high　CO-liberating　rate　of　43.5　mu　mol　mg(-1)　h(-1).　The　in-situ　PL　and　transient　photocurrent　measurements　reveal　that　the　spinel　catalyst　can　hamper　recombination　and　accelerate　transfer　of　light-excited　charge　carriers,　and　thus　boosting　the　CO2　reduction　reaction.　At　last,　a　possible　mechanism　of　the　NiCo2S4-catalyzed　CO2　photoreduction　reaction　is　proposed.