Natural gas in the Mellitah plant contains impurities such as CO2 and H2S. These impurities are undesirable and cause many technical problems. To overcome these problems, an MDEA solution is used with an increase of 100 mm in the height of the absorption column to increase the residence time instead of 50 mm in the original design, which resulted in an increase in cost. The aim of this paper is to use other amines such as DEA, which is a good candidate that can be mixed to MDEA solution doping to increase the reaction rate of MDEA solution with the CO2 sweetening process put under investigation using Aspen HYSYS v.11 as a simulator. In addition, an optimization study was performed by mixing different concentrations of DEA with MDEA and the concentration of each mixture is considered a simulated scenario to achieve the best absorption. Results showed the best possible scenario at the current operational conditions is when the amine feed stream is at a concentration of 39% MDEA and 1% DEA, where it showed better gas quality as the absorption of CO2 and H2S where more efficient. Furthermore, the estimated duty required according the simulator was less by 4.46x104 kw. Keywords: natural gas sweetening, Mellitah gas plant, MEA, DEA, MDEA process simulation, Aspen HYSYS V11.