Ammonia-oxidizing　microorganisms　(AOMs)　play　important　roles　in　nitrogen　removal,　but　their　metabolic　activity　in　winter　months　in　wastewater　treatment　plants　(WWTPs)　remains　unclear.　Here,　two　full-scale　WWTPs　were　selected,　and　a　total　of　48　DNA-based　stable　isotope　probing　(DNA-SIP)　microcosms　of　activated　sludge　samples　at　different　winter　months　(November-January)　and　temperatures　(13　degrees　C,　25　degrees　C　and　37　degrees　C)　were　constructed　to　evaluate　the　temporal　heterogeneity　and　temperature　response　of　active　AOMs.　The　results　provided　direct　evidence　that　the　temporal　heterogeneity　of　AOMs＇　activity　was　not　obvious　in　winter　months.　In　general,　ammonia-oxidizing　archaea　(AOA)　and　bacteria　(AOB)　co-participated　in　the　active　ammonia　oxidation　in　three　winter　months　at　in　situ　temperature　(13　degrees　C)　in　two　WWTPs,　and　AOA　were　the　dominant　active　AOMs,　even　though　AOB　outnumbered　AOA　in　seed　sludge.　In　contrast,　higher　peaks　of　AOA　in　＂heavy＂　fractions　at　25　degrees　C　and　37　degrees　C　also　provided　compelling　evidence　for　the　dominant　contribution　of　AOA　to　active　ammonia　oxidation　under　higher　temperatures.　The　Illumina　sequencing　of　C-13-DNA　obtained　from　the　DNA-SIP　microcosms　at　13　degrees　C　in　three　winter　months　further　suggest　that　Candidatus　Nitrososphaera　evergladensis　and　Candidatus　Nitrosocosmicus　exaquare　were　the　dominant　active　AOA　in　two　WWTPs,　while　the　active　AOB　were　dominated　by　Nitrosomonas　oligotropha.　At　higher　temperatures,　active　AOA　shifted　to　Ca.　N.　evergladensis　and　Candidatus　Nitrososphaera　gargensis,　and　Nitrosomonas　marina,　Nitrosomonas　europaea　and　Nitrosomonas　communis　dominated　in　the　active　AOB.　Overall,　AOA　rather　than　AOB　dominated　the　active　ammonia　oxidation　in　winter　months　and　at　higher　temperatures　in　the　full-scale　WWTPs　tested.