The purpose of this study was to perform basic study on the characteristics of CO₂ Adsorption according to Na₂CO₃, K₂CO₃, Li₂CO₃-impregnated activated carbon in Fixed Bed Reactor. From the results of this study, following conclusions were made: Na₂CO₃, K₂CO₃, Li₂CO₃-impregnated activated carbon which had a longer breakthrough time and more enhanced adsorption capacity than the activated carbon was tested with isothermal adsorption and tested for CO₂ adsorption amount varied with temperature, CO₂ inlet concentration, gas flow rate, aspect ratio, etc. Based on the results, when Langmuir, Freundlich and Dubinin-Polanyi adsorption isotherms were used for linear regression of isothermal adsorption data, Langmuir adsorption isotherm was the most suitable. And, the optimum condition for Na₂CO₃ and K₂CO₃ impregnated activated carbon make-up was 1N and Li₂CO₃ was 0.1N. It could be concluded that adsorption capacity was decreased with adsorption temperature and increased gas concentration. When the aspect ratio (L/D) was varied 0.5, 1.0 and 2.0, the significant drop of adsorption amount was observed below 1.0 and breakthrough time was shortened with gas flow rate.