Abstarct: The development of energy-efficient systems and saline water desalination processes is rapidly increasing due to the ever-increasing demand for water and energy, their consumption in different parts of human life, and the need to reduce environmental pollution. Today, one of the views to achieve the stated goals in this field is the use of simultaneous and multiple production systems. The present study investigated the application of the ejector refrigeration cycles (ERC) launched by the gas turbine waste heat and the use of the produced refrigerant to activate the intercooler between the two compression stages of the Brayton cycle compressors in the combined cycle power plant. Also, the series system of two desalination processes, including reverse osmosis modules and membrane distillation (MD) process, was investigated to increase the extraction rate of freshwater from saline water and reduce the production cost as well as the harmful environmental effects caused by desalination processes. The results demonstrate that using the ERC as an intermediate cooler between the two stages of the compressor has many advantages over the conventional air-conditioning exchangers installed between the compressor’s two stages. The highest thermal and exergy efficiency and the lowest fuel consumption and LCOE values and carbon dioxide production in the proposed power cycle are 62.79%, 60.11%, 114.7 kg/MWh, 27.61 $/MWh, and 316.83 kg/MWh, respectively. In the combined RO/MD desalination process, the results indicate that for the saline water entering the system at a temperature of 25 °C, the amount of recovery and total dissolved solids (TDS) of freshwater produced for RO modules is 39.62% and 276 ppm, and 47.64% and 223 ppm for the proposed combined RO/MD desalination process, respectively. The economic and environmental evaluation of the proposed desalination process shows that if waste heat from power plant cycles is employed as the heat generator required by MD modules for the desalination plant with a capacity of 30000 m^3/day, the freshwater production cost for the combined RO/MD desalination process is 0.872 $/m^3 and 1.42 $/m^3 for MD modules. Also, this combination causes a fall of 11.16% in the costs related to the carbon tax as well as the production and emission of CO_2 when comparing the two methods with each other.