The　three-stage　AO　coupled　biofilm　reactor　was　used　to　treat　low-temperature　wastewater.　At　the　temperature　was　(10±1),　the　hydraulic　retention　time(HRT)　was　controlled　to　8h,　the　inlet　flow　distribution　ratio　was　3:　2:　1,　and　the　sludge　reflux　ratio　was　50%,　then　the　low-temperature　sewage　removal　effect　of　the　coupled　process,　the　change　rule　of　pollutants　in　the　reactor,　the　removal　rule　of　nitrogen　at　each　stage,　and　the　system＇s　nitrification　and　denitrification　performance　were　studied.　The　removal　efficiency　of　COD　and　NH4+-N　in　the　coupled　process　were　exceeded　90%,　and　the　removal　efficiency　of　TN　and　TP　reaches　80%.　Moreover,　the　concentration　of　biofilm　in　the　reactor　ranged　from　400　to　800mg/L,　the　removal　rate　of　NH4+-N　at　all　stage　of　the　system　were　exceeded　80%.　The　denitrification　rate　and　the　rate　of　aerobic　simultaneous　nitrification　were　50.15%　and　26.05%,　respectively.　Affected　by　the　substrate　concentration　and　the　number　of　functional　bacteria,　the　reactor＇s　second-stage　specific　nitrification　rate　and　specific　denitrification　rate　were　the　highest.　©　2020,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.