The solubility of CO2 in aqueous methyldiethanolamine solutions was measured in atmospheric pressure cell and high pressure cell
respectively. The experimental temperature was from 40 to 100℃
CO2 partial pressure was from 1 to 1000 kPa and the concentration of methyldiethanolamine was from 2. 0 to 4. 28 kmol/m3. A simple model and a thermodynamic model which can be used for engineering calculation were established by using the solubility data determined. The heat of solution were calculated from the experimental results with the Gibbs -Duhem equation.