The　intrinsic　nature　of　irreducible　oxides　(e.g.　Al2O3)　makes　it　hard　to　tune　the　charge　state　of　supported　latetransition　metals,　then　difficult　to　adjust　the　selectivity　of　catalysts　in　CO2　hydrogenation.　Herein,　we　find　that　modifying　the　Pd/Al2O3　catalyst　with　alkali　metals　(especially　potassium)　is　efficient　to　boost　the　CO　formation　in　CO2　hydrogenation.　In　comparison　to　Pd/Al2O3,　approximately　twenty-fold　promotion　in　reverse　water-gas　shift　(RWGS)　rate　was　achieved　on　K-modified　catalysts　with　proper　K/Pd　proportions.　Combined　structural　characterizations　demonstrate　that　the　enhanced　Pd-O　interactions　through　K　mediation　stabilize　the　ca.　2　nm　sized　Pd　particles　as　well　as　the　electron-deficient　state　of　Pd,　which　are　robust　enough　during　longtermed　evaluation　with　undamped　performance.　In　situ　spectroscopy　unveils　a　bi-dentate　*HCOO　associated　reaction　mechanism　taking　effect　on　alkali-modified　catalysts,　which　contributes　to　similar　to　100　%　of　CO　selectivity　and　3318.1　mmol.g(Pd)(-1).h(-1)　of　CO　formation　rate　at　340　degrees　C.