Pickling units in mill industry counsumes a greate amount of water for washing and rinsing to purity and separating of scales and impurities. About twenty five cubic meters per hour of waste water is produce in final rinsing step in Mobarakeh steel complex (MSC). The water for final rinsing must be pure that its quality the decrease after usage in this step, therfor the waste water produced in rinsing step can not be recycle and it sent to neutralization unit where the lime is added to it this neutralized water is used for irrigation. Aim of this investigation is upgrade used the rinse water in pickling unit of Mobarakeh Steel Company by evaporator. At first, were measured concentration of hydrochloride acid and amount iron ion in wastewater. The concentration iron and HCl are 0.25-1.5 g/l and 7-9 g/l respectively. wastewater must be pre- treat before enters to evaporator, because iron ion causing precipitation in the evaporator and cause it disable. There are different methods for the pretreatment that in this investigation have used the caustic to neutralize the wastewater and iron removal. 3 and 5 normal caustic soda is used, by adding it almost all of the iron in the effluent comes in the form of precipitation and 15-20% (3-4 ludge is produce. After filtration,16-17 cubic meter of neutralized effluent have entered to evaporator and there have heat transfer by vapour, therefore condensate and transformed to DM water and are using for final rinsing of steel plates. Keywords : DM water, evaporator, Soda, Hydrochloric Acid, Iron