In　this　work,　density　functional　theory　(DFT)　calculations　have　been　employed　to　investigate　the　adsorption　properties　and　reaction　process　of　CO2　hydrogenation　to　CH3OH　on　Cu-based　catalyst　surface　with　different　Ir　doping　ratios.　During　the　reverse　water-gas　shift　(RWGS)　pathway,　CO2　firstly　hydrogenates　to　trans-COOH.　Next,　trans-COOH　isomerizes　to　cis-COOH,　which　will　dissociate　to　CO+OH　subsequently.　Then　CO2　will　consecutively　hydrogenate　to　HCO,　H2CO,　H3CO　and　the　target　product　H3COH.　The　results　show　that　the　formation　of　CO+OH　is　the　rate-determining　step　for　Ir3Cu6(111),　while　the　rate-determining　step　for　Ir6Cu3(111)　and　IrMLCu(111)　is　the　formation　of　HCO,　where　the　energy　barriers　to　be　overcome　are　1.21　eV,　1.35　eV　and　1.34　eV,　respectively.　In　addition,　the　dissociation　of　H2　is　almost　spontaneous　on　IrCu(111)　surfaces,　which　will　provide　a　large　amount　of　H　source　for　the　reaction.　Overall,　this　work　shows　that　the　change　of　Ir　doping　ratio　on　the　surface　of　Cu　catalyst　has　an　pronounced　effect　on　the　hydrogenation　of　CO2　to　methanol,　especially　on　IrMLCu(111)　surface.　Our　results　are　helpful　to　provide　some　references　for　the　design　and　modification　of　synthetic　noble　metal　Ir　doped　Cu-based　catalyst.　©　2022