The aim of this research is performance evaluation of Reverse Osmosis method for treatment of ion exchange resins regeneration wastewater from a petrochemical complex in Iran. Currently this wastewater is discharged to evaporation lagoons after neutralization. Thus, we need to set up a pilot plant which has membrane cell for treatment performance evaluation of three kinds of reverse osmosis membranes. To conduct the study three kinds of membranes (TORAY, CSM, FILMTEC) all for sea water, were used. We must adjust pressure and recovery (cross flow velocity) to obtain the most optimum permeates flux with the lowest Electrical Conductivity (EC). Pressure and recovery have been chosen at three levels and each run of experiment took almost five hours. Therefore, nine experiments have been done for each kind of membrane sample and totally 27 tests have been done to obtain the optimum flux and the minimum EC. The levels are 20, 25 and 30 bar for pressure and for recovery we can choose cross flow velocity 0.27, 0.54 and 0.81 m/s. Results showed FILMTEC membrane has the highest salt rejection percentage .Therefore, the performance of FILMTEC membrane for treating this kind of wastewater is better than the other membranes During this study, EC has been decreased from 14420 to about 470 , under 25 bar pressure and 0.54 m/s cross flow velocity and the permeate flux was 39.1 (l/m2.hr). The percentage of dissolved solids removal is nearly 97 which are preferable. Considering the results of treated wastewater, this treated wastewater can be used for irrigation or other purposes.