Abstarct: Evaluation of fresh water production system using reverse osmosis desalination baxsed on solid oxide fuel cell and Stirling engine has been investigated. Fuel cells are a chemical to electrical energy converter that is nowadays considered as a new technology in energy production, among the available fuel cells, solid oxide fuel cells have great potential for use in cogeneration systems due to their high operating temperatures (700-1000 ° C). Output Heat Solid Oxide Fuel Cells (SOFC) act as a high-temperature heat source that can be used as a heat source for heat engines such as a Stirling engine. The hybrid system consists of a solid oxide fuel cell and a Stirling engine, be a power plant that uses fuel cell output heat to generate power in a Stirling engine, that this recycle heat improves overall system efficiency. Also according to the problems of water scarcity in the world and the need for freshwater, reverse osmosis desalination systems have become very common, that in this study, we investigated a hybrid fuel cell-Stirling engine and desalination system that the system is a freshwater manufactured product. In this research, important objective functions such as power and exergy destruction density and exergy and energy efficiencies are investigated. Overall, this research investigates the performance of a hybrid system fuel cell-Stirling engine and reverse osmosis desalination for production freshwater that first done a thermodynamic analysis for all components of the system, therefore by a multi-objective optimization of the performance of the hybrid power generation system fuel cell-Stirling engine, the amount of water produced for reverse osmosis desalination has been calculated. The modeling results show that in a constant current density with increasing temperature the amount of power and efficiency of solid oxide fuel cell increases, and also, by decreasing the leakage resistance, the amount of power and efficiency of the solid oxide fuel cell increases, and besides, in a constant current density, by increasing the molar fraction of H2 and decreasing the molar fraction of H2O, the amount of power and efficiency of the solid oxide fuel cell increases. In a constant current density, as the pressure increases, the amount of power and voltage increases. The results show that, The highest amount of power in the hybrid system is 7747 and also the highest value of exergy destruction density is 36170 and maximum efficiency is 0/77 and the exergy destruction density is 36170 and the energy and exergy efficiency is 0/86, also the maximum volume is obtained at the mass flow rate of freshwater is 3 kg/s.