The　doping　of　metals　onto　the　inorganic　non-metallic　catalyst　g-C3N4　facilitates　the　reduction　of　CO2　to　C1　and　C2　products,　representing　an　effective　method　for　reducing　atmospheric　carbon　dioxide　and　mitigating　global　warming.　This　paper　investigates　the　stability　and　catalytic　activity　of　g-C3N4　doped　with　Fe,　Co,　Ni,　and　Cu　using　density　functional　theory　(DFT).　The　optimal　reduction　pathways　of　CO2　at　different　metal　sites　are　analyzed.　The　results　show　that　bimetallic　doping　exhibits　a　synergistic　effect　compared　to　traditional　metal　doping,　significantly　enhancing　the　visible　light　response　range　of　g-C3N4,　promoting　the　adsorption　and　activation　of　CO2,　and　lowering　the　Gibbs　free　energy　barrier　of　the　reduction　intermediates.　Of　the　materials　studied,　Co2@g-　C3N4　and　Ni2@g-C3N4　require　higher　energy　and　show　poor　CO2　activation　performance.　In　contrast,　Fe2@g-　C3N4＇s　site1　and　site2　display　superior　catalytic　performance　with　activation　energy　barriers　of　0.74　eV　and　0.78　eV,　respectively.　Cu2@g-C3N4,　on　the　other　hand,　shows　favorable　performance　only　at　site1,　with　an　activation　energy　barrier　of　0.63　eV.　This　catalyst　is　expected　to　serve　as　an　effective　tool　for　CO2　reduction,　providing　a　new　strategy　for　the　design　and　development　of　more　efficient　and　selective　CO2　reduction　catalysts.