High COD concentrations in effluent, high membrane loading, and frequent congestion on the membrane are three common shortcomings of treating landfill leachate using the biodegradation technique. Accordingly, advanced treatment of the bio-chemical effluent of landfill leachate by Fenton oxidation combined with coagulation technique were performed in this study. The experiment was designed with the response surface method (RSM) considering three factors, i.e., the dosages of polymeric ferric sulfate (PFS), n(H₂O₂)/ n(Fe²⁺), and H₂O₂. Experimental results show that the fitting curve has high significance and sensitivity, and the prediction error of the COD removal rate is smaller than ±5%. The results also show that H₂O₂ has the greatest influence on COD removal rate, while PFS has the smallest. The optimal operating conditions for landfill leachate with a COD concentration of 2,000 mg/l are: the dosages of PFS (the concentration is 0.05g/ml), and H₂O₂ (30%) and n(H₂O₂)/n(Fe²⁺) are 67 ml, 17 ml, and 6 respectively. The optimized COD removal rate can reach as high as 92.11%.