Cd-doped　ZrO2　catalyst　has　been　found　to　have　high　selectivity　and　activity　for　CO2　hydrogenation　to　methanol.　In　this　work,　density　functional　theory　calculations　were　carried　out　to　investigate　the　microscopic　mechanism　of　the　reaction.　The　results　show　that　Cd　doping　effectively　promotes　the　generation　of　oxygen　vacancies,　which　significantly　activate　the　CO2　with　stable　adsorption　configurations.　Compared　with　CO2,　gaseous　H-2　adsorption　is　more　difficult,　and　it　is　mainly　dissociated　and　adsorbed　on　the　surface　as　[H-Cd-H-O]*　or　[H-Zr-H-O]*　compact　ion　pairs,　with　[H-Cd-H-O]*　having　the　lower　energy　barrier.　The　reaction　pathways　of　CO2　to　methanol　has　been　investigated,　revealing　the　formate　path　as　the　dominated　pathway　via　HCOO*　to　H2COO*　and　to　H3CO*.　The　hydrogen　anions,　H-Cd*　and　H-Zr*,　significantly　reduce　the　energy　barriers　of　the　reaction.