Abstract: Combination of Fenton reagent and potassium monopersulfate was applied to treat bilge water and the optimal conditions were determined by variable control method. The results showed that at pH=3, the chemical oxygen demand (COD) of bilge water decreased from 963mg/L to 120mg/L after three-time flocculants by Fenton reagent (30%H₂O₂ 19.2mL/L, FeSO₄ 5.21g/L, and nFe²⁺/nH₂O₂=0.0997), up to 87.54% of COD was removed.The suspected H₂S smell in the water was also disappeared, and the water color became transparent from dark-brown and opacitas. After flocculants, the water sample was oxidized by potassium monopersulfate. Under acidic condition, the potassium monopersulfate had the highest oxidized efficiency at 50~60℃. The organic matter in the bilge water was degraded significantly when the adding amount of potassium monopersulfate was 1.3 times as the theoretical amount. Then the COD in the bilge water decreased from 120mg/L to 20.5mg/L and the removal efficiency was 82.35%. Finally, the COD removal efficiency reached 97.82% after the bilge water was treated by the combination of Fenton reagent and potassium monopersulfate, and the COD concentration matched national wastewater discharge standard.