Phosphoric ester flame-retardant wastewater is a kind of organic wastewater that is hard to treat because of its high concentration of COD with refractory biodegradable components. Based on these characteristics, the Fenton oxidation technique was used in this study for the treatment of phosphoric ester flame-retardant wastewater. The treatment effect was evaluated through detection of the change of COD concentration. The effects of dosages of FeSO₄·7H₂O and H₂O₂ as well as pH adjustment with different acids in the treatment were investigated. The results show that the optimal conditions for the technique are as follows: dosages of FeSO₄·7H₂O and H₂O₂of 5g/L and 5. 55g/L, respectively. In addition, sulfuric acid is superior to hydrochloric acid in pH adjustment.