Abstract: Oxidative foam decontamination waste liquid could not be treated directly due to high levels of organic compounds. In order to solve this problem, Fenton oxidation method was applied for the first time to degrade organic compounds in foam decontamination waste liquid, which provided a new idea for the pretreatment. Fenton oxidation method and two-step combined degradation process were adopted. The effects of various process parameters on COD removal rate of foam decontamination waste liquid and the suitable operating conditions of each degradation process were explored in this study. The results show that under the suitable operating conditions of initial degradation, Fenton oxidation method can reduce the COD of waste liquid from (37 000±1 850) mg/L to (2 064±95) mg/L(n=3), with a COD removal rate of up to (94.40±0.54) %(n=3). However, the residual liquid with COD of (2 064±95) mg/L still do not meet the conditions of existing methods of waste liquid treatment. Under the suitable operating conditions of second degradation, Fenton-UV combined method can continue to reduce the COD of residual liquid from (2 064±95) mg/L to (478±12) mg/L, which meets the conditions of existing methods of waste liquid treatment. In conclusion, Fenton oxidation method and two-step combined degradation process are suitable for the pretreatment of oxidative foam decontamination waste liquid.