Solubilities of CO2 in aqueous mixtures of methyldiethanolamine (MDEA) and piperazine (PZ) have been measured for temperatures and CO2 partial pressures ranging from 30 to 90 degrees C and 13.16 to 935.3 kPa, respectively. A modified Deshmukh-Mather thermodynamic model is used to correlate the experimental data with the average deviation of 9.8%, in which the effect of salts on Henry＇s constant is taken into consideration. The results also indicate that the second-order dissociation reaction for piperazine can be neglected. A simple model is also given with the average deviation of 11.6%.