Anaerobic　ammonium　oxidation　is　an　important　part　of　the　biological　nitrogen　removal　process,　and　the　performance　of　the　process　is　determined　by　the　microbial　community　structure.　Low-temperature　anaerobic　ammonium　oxidation　technology　has　good　prospects　for　saving　a　lot　of　energy,　and　anaerobic　ammonium　oxidation　bacteria　play　a　vital　role　in　the　removal　of　total　nitrogen　from　waste　water.　To　explore　the　microbial　community　structure　changes　of　anammox　reactor　in　sewage　treatment　during　the　cooling　process　(from　30℃　to　20℃),　the　total　amount　of　the　microbial,　the　quantity　of　anaerobic　ammonium　oxidation　and　the　change　of　functional　microbial　community　were　investigated　in　a　sewage　treatment　process　using　the　phospholipid　fatty　acid　method　(PLFA),　quantitative　PCR　and　the　clone　library　of　bacterial　16S　rRNA.　The　PLFAs　results　showed　that　the　total　amount　of　microbial　was　first　decreased　and　then　gradually　increased　with　the　running　time,　when　the　temperature　dropped　from　30℃　to　20℃,　and　the　NH4+-N　content　in　the　effluent　of　the　system　was　decreased.　The　quantitative　PCR　results　showed　that　16S　rRNA　gene　copies　of　anammox　bacteria　increased　from　1.19×108　copies·mL-1　to　1.86×108　copies·mL-1　in　the　wastewater.　The　PCR-DGGE　results　showed　that　when　the　temperature　decreased,　the　anammox　bacteria　were　further　enriched.　A　shift　of　anammox　bacteria　community　from　single　Candidatus　Kuenenia　sp.　to　a　combination　of　Candidatus　Brocadia　sp.　and　Candidatus　Kuenenia　sp.　was　observed.　©,　2015,　Science　Press.　All　right　reserved.