Today, improving the elimination of refractory pollutants in landfill leachate through electrochemical oxidation technology has attracted considerable attention. In this study, a combination of anodic oxidation and cathodic coagulation process using Ti/RuO₂–IrO₂ and Al electrodes, was adopted to treat the mature landfill leachate with a very low biodegradability ratio (BOD₅/COD) of 0.12. The effects of current density, pH, and the chloride ion concentration on the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH₃–N) were investigated by response surface methodology (RSM). The optimum condition of 83.7% COD and 100% NH₃–N removal was achieved with a current density of 0.1 A cm⁻² and a pH of 6.37, the chloride ion concentration 6.5 g L⁻¹, and an electrolytic time of 150 min. In addition, heavy metals were partly removed. A main degradation mechanism of the pollutants, including oxidation, coagulation and precipitation, was elucidated by gas chromatography-mass spectrometry (GC-MS), environmental scanning electron microscopy coupled with energy dispersive spectrometer (ESEM/EDS) and Fourier transform infrared spectroscopy (FT-IR) analysis of organic components in landfill leachate and sludge generated at the cathode. These results indicated that the electrochemical processes could be a convenient and efficient method for the treatment of landfill leachate.