In order to treat the acidic washing water in the industrial production， heterogeneous photo-fenton degradation-blowing off is proposed. Firstly， the magnetic catalyst Fe²⁺-Fe₃O₄@AC was prepared by coprecipitation-impregnation. Then，the degradation of NTO in the washing water （about 4 g·L^-1） with system （UV/Fe²⁺-Fe₃O₄@AC/H₂O₂） was studied. pH， addition of H₂O₂ and catalyst concentration were screened to obtain the best conditions. Five repeated experiments were carried out to study the catalyst stability. The importance of conditions， free radical quenching experiment and the EPR spectrum results were studied to speculate on a possible degradation mechanism. In the process of degradation under optimal conditions and blowing off， the change of COD and NH₃-N were recorded.The results show that this system can degrade NTO efficiently. When pH is 2， n_H2O2∶n_NTO is 5 and catalyst concentration is 1 g·L^-1， 99% of NTO can be removed in 150 min. The catalyst has good stability and the NTO removal rate can still reach 82% after 5 cycles. The removal rate of COD and NH₃-N are both 99% after degradation and blowing-off.·OH and ·O₂^- make a contribution to degradation and ·OH plays a major role.