Aiming at the treatment of petrochemical RO concentrated water, the technique of O₃-photodegradation-carbon fiber was used to treat the wastewater from a petrochemical corporation in Tianjin and a pilot-scale experiment was carried out. The results show that the optimum pH value is 8~9 and the optimum concentration of O₃ is 10. 0~13. 3 mg/L. COD concentration of the final effluent is less than 40 mg/L, the maximum NH₃-N removal rate is 44. 6%, and the SS reaches the first grade discharge standard. The operating cost of RO concentrated water is 2. 1 CNY per ton. The removal rate of NH₃-N can be increased by increasing the internal reflux ratio. When the pH value of the intake water of the carbon fiber device is 8, the adsorption efficiency is the highest.