Amino acid ionic liquids (AAILs) including 1-butyl-3-methylimidazolium glycinate ([Bmim][Gly]), 1-butyl-3-methylimidazolium L-lysinate ([Bmiml[Lys]) and tetramethylammonium glycinate ([N-1111] [Gly]) were used to enhance the absorption of CO2 in N-methyldiethanolamine (MDEA) aqueous solutions. The mole fractions of CO2 in N-2 + CO2 gas mixtures ranged from 0.2 to 1.0. The mass fractions of MDEA and AAILs respectively ranged from 0300 to 0.400 and 0.050 to 0.100. The absorption capacity and absorption rate under series of conditions were presented and the influences of CO2 partial pressure and the types of AAILs on the absorption performance were demonstrated. (C) 2017 Elsevier Ltd.