Abstract: A combined process of a stage upflow anaerobic sludge blanket (UASB1), an anoxic/aerobic (A/O) reactor and a rear UASB (UASB2) was used to treat actual landfill leachate. This process only used the residual organic matter and internal carbon as the carbon source to completely remove the organic matter, total nitrogen and ammonia nitrogen. The factors affecting the partial nitrification were also investigated. The influent leachate of the system was mixed by raw leachate and domestic wastewater in a ratio of 1:5. The organic matter, total nitrogen and ammonia nitrogen of the influent leachate of the system were about 1700-1800,0-700 and 650-680 mg/L, respectively. The experimental results showed that the organic matter, total nitrogen and ammonia nitrogen removal efficiencies were higher than 95%, and the total nitrogen concentration of final effluent was about 38 mg/L, which was less than the requirement of the latest national emission standard. In addition, the combined inhibition action of the FA (free ammonia) and FNA (free nitrite acid) to the NOB was the major reason for the stable partial nitrification higher than 80% of the nitrite accumulation ratio in the A/O reactor. On the whole, the integrative process could completely remove the nitrite and nitrate produced by the nitrification in the aerobic zone of the A/O reactor and realize advanced nitrogen removal.