An exergoeconomic optimization of a double effect thermal vapor compression desalination system is performed. This unit is integrated in the thermal power plant of Phosphoric Acid factory owned by The Tunisian Chemical Group. The daily production of this unit is about 528 m(3) of fresh water. A mathematical model based on energy, exergy and economic balances is established using EES software. Multi-objective optimization is carried out in the purpose to obtain the maximum exergy efficiency with minimum production cost. The effects of the main operating parameters on the desalination unit performances are analyzed. Obtained results show that, the maximum exergy efficiency is obtained for the evaporator II followed by the distillate and brine pumps. The condenser has the lowest exergy efficiency. The thermocompressor is the major contributor in exergy destruction. The mass flow rate and the pressure of the motive steam affect positively the GOR. The SPECO method is used to perform the economic optimization. The maximum exergoeconomic factor f is obtained for the evaporator H followed by the evaporator I, the thermocompressor, the distillate pump and the condenser. The optimum operating conditions leading to suitable overall exergy efficiency with low production cost of distillate water are determined.