In this book Sweetening of natural gas is accomplished via cordial litterateur review, variety methods of engineering design and modern simulation software. Furthermore, the literature review examines and discusses several natural gas sweetening methods by consulting the most recent engineering books and papers and it is selected the most appropriate and economical method in practical gas industry side to be applied for design calculations and simulation part. Moreover, the calculation design section is examined three different sources of sour gas streams which are selected from real hydrocarbon reservoir data and it successfully achieved high acid gas removal processes design by achieving various design calculations for example, material and energy balance, amine circulation rate calculations, contractor tower design. Engineering softwares are also used to remove acid gases from raw natural for example, Aspen HYSYS® V.7.3 simulation program. Furthermore, mathematical optimisation is also applied in this study for various design calculations including amine circulation rate and solvent type selection.