Integrated thermal desalination unit and gas turbine is a new achievement in energy engineering considerations. In this research, two study cases have been computed for mentioned system. For the first case [Y. Wang, N. Lior, Desalination 214 (2007) 306-326], grass root design of desalting plant has been applied by code developing in EES (Engineering Equation Solver) software. Then, changes in quantitative and qualitative parameters have been investigated for different types of systems. In order to find an economical amount, an optimization code has been developed in GAMS (Generalized Algebraic Modeling System) software. According to results, a desalting system with three effects is the best choice in this case at all. {0.52 (kg/s) distillate production, 113 (m(2)) total heat transfer area, 76.69 (kW) total exergy destruction and 1.98 ($/m(3)) unit product cost}. In the second case, feasibility of integration has been investigated by retrofit viewpoint for Lavan Island. As a result of simulation, thermal energy recovered by HRSG (Heat Recovery Steam Generator) has been equal to 4728 (kW). It shows a great potential for motive steam generation plus to 2.77 (kg/s) distillate productions. The amount of 105,494 ($/yr) cost reductions is concluded optimization procedure for substitution of boiler with HRSG. (C) 2010 Elsevier B.V. All rights reserved.