Through analyzing the basic characteristic of red mud from an aluminum factory in Shanxi, a dealkalization simulation experiment of red mud with lime kiln tail gas containing CO2 around 20% is proposed. Thermodynamic analysis shows that dealkalization by using lime kiln exhaust is feasible, and the actual main factors affecting dealkalization are the dynamics factors. Experiments take dealkalization rate as an index, the influence of liquid-solid ratio, CO2 volume fraction, CO2 mole ratio, stirring speed and reaction temperature of red mud on dealkalization rate are researched and the results are as follows. The reasonable parameters for dealkalization are liquid-solid ratio 8 mL/g, CO2 volume fraction 20%, CO2 mole ratio 40, stirring speed 400 r/min and reaction temperature 60 ℃, and the dealkalization rate under these process conditions is 31.10%. The study results show that lime kiln tail gas of containing CO2 at around 20% could be used for red mud dealkalization treatment, and this process can remove the soluble alkali in red mud, which conforms to the concept of “using waste treat waste”.