Abstract: To elucidate the competitive adsorption mechanisms of CO/CO₂ versus H₂ on carbon steel surfaces with vacancy defects, first-principles calculations and molecular dynamics simulations were employed to investigate the adsorption behaviors of CO, CO₂, and H₂ on both defect-free and vacancy-containing α-Fe(110) surfaces. The results indicate that CO exhibited a significantly lower adsorption energy on the surface (-1.94 eV) than H₂ (-1.35 eV) and CO₂ (-0.65 eV), and CO/CO₂ inhibited H₂ adsorption by suppressing surface electron activity. Under a total pressure of 10 MPa and hydrogen partial pressures of 1, 2, and 3 MPa, the addition of 0.1 MPa CO₂ reduced the peak values of relative molecular concentration of H₂ on the α-Fe(110) surface by 40.3%, 57.6%, and 50.6%, respectively. In contrast, blending with 0.1 MPa CO resulted in significantly greater reductions of 65.9%, 69.4%, and 70.6% under the same conditions. When the vacancy concentration was 1.0% and the hydrogen partial pressure was 2 MPa, the presence of 0.1 MPa CO and CO₂ impurities resulted in an increase in the peak relative molecular concentration of H₂ on the α-Fe (110) surface by 38.5% and 42.3%, respectively.