In order to improve the treatment efficiency of the high concentration of ammonium nitrogen in landfill leachate, anaerobic baffled reactor (ABR) and hybrid biofilm reactor (HBR) were introduced to the full-scale treatment of Datianshang landfill leachate. The efficiencies of nitrogen removal and the status of microorganism of the two biological treatment processes were analyzed. To achieve ANAMMOX and partial nitritation process, the concentration of dissolved oxygen in HBR was controlled and the effluent of HBR was recycled to the inlet of the ABR in a large proportion. The full-scale operation results showed that when the concentration of influent ammonium nitrogen was at 336.24 - 685.09 mg/L, the anaerobic granule sludge and the ANAMMOX bacteria were observed and the average ammonium nitrogen removal rate reached 34.9% in ABR after the start-up period of 60 days. The population of ammonium oxidizing bacteria and the average ammonium nitrogen removal rate in HBR reached 6.4 x 10(7) cells/mL and 95.1%, respectively, after 30 days of ABR stable running process. The final effluent ammonium nitrogen concentration was under 25 mg/L and the removal rate of total nitrogen was above 80% after the ABR-HBR combined processes treatment. It was suggested that using of advance environmental biotechnology to improve the capacity of the conventional leachate treatment plant was advisable, especially for those low efficiency facilities working improperly.