Abstarct: A large part of earth is covered with water, but a large proportion of it is way too salty for any domestic or industrial use, leaving only 2.5% of it fresh water. Growing demand for fresh water alongside with depriving the natural water sources, is one of the most difficult problem that involves different parts of our world. Therefore, desalting the sea water or brackish water, is being used wildly in arid areas. Today, thermal and membrane technologies are the most common desalination processes. Desalination is considered as an expensive process and the costliest part of a desalination module is related to providing the necessary energy. Furthermore, and in recent years, the global usage of energy is rapidly increasing, mostly because of the growing rate of population and emerging new powers. cogeneration means producing two or more products from the same primary energy source, which is more affordable. In this research, First, different type of desalination process, including reverse osmosis (RO), Nanofiltration (NF) and multi effect distillation (MED) are vividly modeled and governing equations are extracted. Then, with the use of softwares like Matlab and EES, the performances are modeled and the results are validated. For further validation (for membrane types) an analysis has been conducted via ROSA software. At the end, a novel configuration of poly generation, including gas turbine, dual pressure HRSG for extracting the exhaust gas from gas turbine in low and high pressure to use in desalination units and refrigeration cycle, is presented, which have all the necessary outputs like cooling, heating, power and water for local use. The results show that with 0.51 kg/s fuel and 20 cubic meter of sea water per hour as inputs, the presented model has the capacity to produce 49.62 kW of cooling capacity, 101.64 kW of heating load, 153.33 kW of net power and 5.8 cubic meter of fresh water per hour. Finally, to consider the effects of design parameters on the outputs of the system, a parametric analysis was further conducted. Also, effect of salinity and flow rate of feed water on hybrid plant thermodynamics restrictions are studied.