Abstarct: The average efficiency of steam power plant in Iran is about 39.2%, which in case of recovering the wasted energy of power plants, a large amount of fossil fuel consumption costs will be saved. In the current study, the focus is on the Iranshahr steam power plant, located in the southeast of Iran, in order to desalination some of its effeluent streams, which include salt water and cooling tower blowdown. By recovering a part of the wasted energy from boiler blowdown, the required steam for the thermal energy needed by the multi-stage flash desalination (MSF) unit is provided. The combination of desalination unit and steam power plant, in addition to saving costs due to fuel consumption, will reduce the emission of carbon dioxide into the atmosphere. To simulate the process, Thermoflow-GT master 23 which is a specialized software for power plants, has been used. Three different scenarios are considered in the simulation, which include the amount of available steam (scenario I), available cooling tower blowdown (scenario II), and available cooling tower blowdown with reduction of cooling tower temperature (scenario III). According to the simulation results, the second scenario has been introduced as the most optimal option. Due to the limitations of the software, the modeling of MSF desalination unit for low capacity has been done in MATLAB software with using the thermodynamic laws, mass balance and heat transfer equations. In conventional MSF desalination unit, a stream of salt water is used for both desalination and cooling purposes. In the present study, a new proposed configuration for the desired desalination process, proportional to the salt concentration of the feed streams and baxsed-on un-mixing of the target streams has been presented. The proposed model in order to produce 92.34 m3/day of fresh water with GOR equal to 3.12 from power plant effeluents, in the seven-stages MSF desalination, requires 775436.7 m3 of natural gas annually. Due to the recovery of 0.47 kg/s from the boiler blowdown, the cost of fossil fuel consumption has been saved, and in terms of environmental considerations, it will reduce the annual production of 1167.57 tons of CO2 into the atmosphere. The cost of each cubic meter of fresh water produced baxsed on the proposed desalination unit is calculated as 0.69 $.