In order to investigate the anaerobic ammonium-oxidation (Anammox) nitrogen removal pathway of the aged refuse bioreactor treating landfill leachate, a lab-scale bioreactor was established and run for 35 weeks, the performance of the bioreactor and its bacterial community structure of Planctomycetes were analyzed. The results showed that the average TN removal rate of landfill leachate could be reached to 89%. 16S rRNA gene library of Planctomycetes revealed that Anammox sequences accounted for 28.3% of the total Planctomycetes sequences in the bioreactor, and previously recognized Anammox bacterium Candidatus Kuenenia stuttgartiensis was the only detected Anammox species in the reactor. It was also found that Anammox bacteria distributed at different sites of the bioreactor while mostly concentrated in the middle and low-middle part. Results above confirmed that Anammox process could happen in aged refuse bioreactor treating landfill leachate and provided an alternative nitrogen removal pathway in practical landfills. (C) 2013 Elsevier Ltd. All rights reserved.