This study attempted to the enrichment of indigenous ANAMMOX bacteria from conventional denitrification tank sludge in landfill leachate treatment plant and also performed the assessment of nitrogen removal efficiency and microbial community analysis. At 807 days after the operation of reactor, it was possible to observe the reddish sludge like a biofilm formation in outflow tubing, as well as the radical removal of the substrate. ANAMMOX bacteria were successfully enriched that total nitrogen removal efficiency and nitrogen removal rate showed 67.6%, 14.4 kg-N/m3·d for assumed ANAMMOX bacteria from reddish biofilm. The analysis of microbial community showed that 19,708 clones were affiliated with ANAMMOX bacteria of Planctomycetes phylum(22.5%) including Candidatus Jettenia(18,911), Candidatus Anammoxoglobus(7) and Candidatus Brocadia(4) genera. The above results mean that ANAMMOX bacteria can also be enriched in the outside of reactor rather than inside and further study need for precise reasons.