Many researches have been performed for CO₂ capture from various industrial gas streams in order to reduce the contribution of CO₂ to global warming. Although being the most effective for CO₂ capture, the chemical absorption process based on amines such as monoethanolamine (MEA) is still too expensive to apply for large CO₂ sources like power plants. In addition, it has been well known that the amine process has inherent problems such as absorbent degradation by acidic compounds and oxygen in gas stream, high energy consumption, and equipment corrosion. Recently, aqueous ammonia has been suggested as a new absorbent which can avoid the above problems. The aqueous ammonia has larger theoretical capacity of CO2 compared to amine solution, low regeneration energy required, low material cost, and potential ability to capture acidic gases in flue gas as well. However, there are only few research reports available in the use of aqueous ammonia for CO₂ capture. Thus, the characteristics of CO₂ absorption into ammonia have not been fully investigated and it requires further in-depth study. In this work, the effects of temperature and concentration of aqueous ammonia on CO₂ absorption capacity were investigated using a semi-batch reactor, and the concentration changes of carbon containing species (ammonium carbonate, ammonium bicarbonate, and ammonium carbamate) during the absorption were also studied using Raman spectroscopy. The bubbling enhanced feature of the reactor reduced the gas-liquid mass transfer resistance remarkably. Hence, the CO2 gas could be absorbed more rapidly into aqueous ammonia. The extremely sharp breakthrough curves were obtained by the reactor and the breakthrough point at given condition was used for interpreting characteristics of CO₂ absorption into aqueous ammonia.