A novel kind of CO₂ solid adsorbents (xLDH/MA, x is the loading of LDH) was prepared by loading of layered double hydroxides (LDH) on the mesoporous alumina (MA) support. The LDHs in xLDH/MA were evenly distributed on the surface of MA. xLDH/MA possessed a large BET surface area (278–378 m²/g), narrow pore-size distribution (4.37–6.23 nm), and a highly crystalline framework. Among all of the samples, 30LDH/MA showed an excellent CO₂ adsorption capacity at 50 °C (1.56 mmol/g), which was 1.55 times larger than that of unmodified MA. Due to the synergistic effect between MA and LDH, 30LDH/MA exhibited a higher surface area and a more amount of adsorption sites, which were the main factors improving its CO₂ adsorption performance. The adsorption process of CO₂ on xLDH/MA was dominated by the chemical adsorption, and the adsorbed CO₂ was mainly stored in the form of carbonate. In addition, the 30LDH/MA composite material showed fast adsorption kinetics and good regeneration efficiency. We believe that such a kind of porous alumina-supported layered double hydroxides would have a great potential in the applications for the adsorption of CO₂.