Carbon dioxide was absorbed into an aqueous solution containing two reactants of 2-amino-2-methyl-1-propanol (AMP) and 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0-3.0 kmol/m3 of AMP, 0-0.2 kmol/m3 of DAM, and 298.15-323.15 K at 15% of CO2 and 101.3 kPa. Diffusivity, Henry constant and mass transfer coefficient of CO2 in the mixed solution of AMP and DAM were used to calculate the theoretical enhancement factor of CO2, which was obtained by an approximated solution of mass balances with the instantaneous and fast regime in CO2-AMP-DAM system. The method of the classification of the chemical regime in the heterogeneous system was used to determine the enhancement factor by adding DAM under the limited concentration of AMP.