Effluent　quality　deterioration　caused　by　seasonal　temperature　reductions　in　wastewater　treatment　systems　using　partial　anammox　technology　is　a　challenge　that　cannot　be　ignored.　Here,　relationships　of　denitrification　and　anammox　under　decreasing　temperature　were　investigated　in　an　anoxic　moving　bed　biofilm　reactor　(MBBR).　Compared　with　stable　partial-denitrification　(NO3-　-*　NO2-),　the　NO2-　reduction　to　N2　was　considerably　inhibited　when　the　temperature　decreased,　conversely　helping　to　the　competition　of　NO2-　for　anammox.　Namely,　this　transformation　provided　sufficient　substrates　for　anammox　bacteria.　Although　the　TIN　removal　decreased　slightly,　anammox　contribution　was　robustly　maintained　at　91.3　+/-　6.6　%,　even　increased.　High-throughput　sequencing　results　revealed　that　anammox　bacteria　were　enriched　(0.56　%　to　1.22　%).　Moreover,　qPCR　results　showed　that　increased　ratio　of　hzsB/(nirK　+　nirS)　further　supported　anammox　gained　an　enhancement.　This　study　demonstrated　partial-denitrification/anammox　process　using　anoxic　MBBR　could　maintain　stable　autotrophic　nitrogen　removal　contribution　when　encountering　temperature　decrease,　providing　a　new　perspective　on　the　application　of　mainstream　anammox.