In order to make the treated gas field water meet the national secondary discharge standard，the corrosion inhibitor CPI-W was firstly added to the simulated gas field water to investigate the effect of corrosion inhibitor on chemical oxygen demand （COD）in gas field water，and then the simulated gas field water added with corrosion inhibitor CPI-W was treated by sodium hypochlorite method，Fenton's reagent method and potassium persulfate-ferrous sulfate method to investigate the COD removal effect，respectively. The results showed that all three treatment methods were able to achieve COD values of simulated gas field water spiked with 1000 mg/L corrosion inhibitor to meet the secondary discharge standard（<150 mg/L）of the comprehensive wastewater discharge standard. After treatment by sodium hypochlorite oxidation method，the COD removal rate reached 94.4% when the sodium hypochlorite dosage was 8 mg/L；after treatment by Fenton's reagent method，the COD removal rate reached 96.1% when the H₂O₂ dosage was 4 mg/L and FeSO₄·7H₂O dosage was 0.08 mg/L；while after treatment by potassium persulfate-ferric sulfate method，the COD removal rate was 97.4% when K₂S₂O₈ was added at 8 mg/L and FeSO₄·7H₂O was added at 4 mg/L. Comparing the COD removal rate and the cost of chemicals，the potassium persulfate-ferrous sulfate method was the best method to degrade the corrosion inhibitor in gas field wastewater among the three advanced oxidation techniques.