Treatment of the sour natural gas is a major step in natural gas processing so that the acid gases such as H2S and CO2 are removed from natural gas stream. The acid gases are harmful to environment and destroy the production equipment so that their presence in gas stream leads to corrosion and lowering heating value. On the other hand, for reliable and optimum design of separation equipment, primarily sufficient and accurate equilibrium data of the acid gases solubility in the aqueous alkanolamines is required. In this work, the simultaneous solubility of the H2S + CO2 in the alkanolamine mixtures is measured at 343 K and total pressure range of 0.1-2.1 MPa. The blends are studied as the aqueous mixtures of N-methyldiethanolamine (MDEA) + 2-amino-2-methyl-1-propanol (AMP) + Piperazine (Pz) and the aqueous mixtures of diisopropanolamine (DIPA), AMP and Pz. For the acid gas solubility measurements, a high pressure static apparatus is used through a volumetric method. The mass fraction of the total alkanolamine is fixed at 0.45 and the results are presented as the partial pressure of each acid gas against its loading (mole acid gas/total mole amine) and mole fraction. The influence of the AMP and Pz on the aqueous DIPA-based and MDEA-based systems are studied so that it is observed that the absorption of the CO2 in the aqueous alkanolamine enhances through separate blending of the AMP and Pz with the aqueous system of MDEA or DIPA and the absorption of the H2S reduces in both of the aqueous DIPA-based and MDEA-based systems. (C) 2014 Elsevier B.V. All rights reserved.