In the paperSH-A process was used for the treatment of mature landfill leachate, which contains high organic content, complex component, high toxicity, poor biochemical purification ability and high ammonia nitrogen. The influence of temperature and the nitrite nitrogen-ammonia nitrogen reaction ratio on the denitrification rate of waste leachate was studied separately. In aerobic section, organic nitrogen was converted to part of the ammonia nitrogen, while ammonia nitrogen was converted to nitrite nitrogen and nitrate nitrogen, which was named complete nitrification reaction. In anaerobic section, the denitrification reaction and anaerobic ammonia oxidation was conducted. On the optimal conditions, the synergistic effect the complete nitrification denitrification and anaerobic ammonia oxidation was conducted to remove ammonia nitrogen of mature landfill leachate. On the condition that the temperature of aerobic period of was 35˚C to 40˚C, temperature of anaerobic period was 30˚C to 40˚C, nitrite nitrogen-ammonia nitrogen reaction ratio was 1.1:1 ~ 1.2:1, and the total nitrogen removal efficiency maintained comparable high and stable.