The implementation of reverse osmosis (RO) process is a solution for increasing water demand. In this work the treatment feasibility of effluent wastewater in Tabriz Petrochemical Complex was evaluated using RO pilot plant. After a pretreatment with cartridge filters, wastewater was introduced to RO unit with a rate of 2000-12,000 l/h. The permeated rate was 600-1500 l/h using different applied pressures of 5-22 bars. The results showed that Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Conductivity, Total Dissolved Solid (TDS), color, turbidity, SO(4), NH(4), Calcium Hardness (CaH), Total Hardness (TH), suspended solid (SS) and SiO(2) of the wastewater were decreased and removed extensively using RO membranes. The flux of permeated stream and the recovery rate were increased with the feed pressure. However the optimum operating pressure for the reverse osmosis pilot was determined as 15 bars leading to a recovery rate of 45%. The results indicate that achieving the "Zero Discharge" goal is possible using RO system. The plan for zero discharge is conducting the concentrated waste from the reverse osmosis system to evaporation pond.