Integrated　anaerobic/anoxic/oxic　process　with　biological　aerated　filter,　AAO-BAF　system　was　used　to　treat　domestic　wastewater　with　low　C/N　ratio　of　about　4.　By　adjusting　influent　flow　rate　of　the　AAO　reactor　and　aeration　rate　of　BAF,　the　effect　of　hydraulic　retention　time　(HRT)　and　aeration　rate　on　the　performance　of　the　AAO-BAF　system　was　investigated.　The　results　showed　that　air/liquid　ratio　and　hydraulic　load　rate　(HLR)　of　BAF　had　great　influence　on　NH4+　removal.　At　air/liquid　ratio　3:1,　NH4+　removal　rate　decreased　to　72%.　Further,　when　HRT=4　h　and　HLR　of　BAF　was　3　m3　·　m-2　·　h-1,　NH4+　could　not　be　removed　completely　even　with　a　high　air/liquid　ratio　of　8:1.　This　work　confirmed　that　there　was　an　obvious　relationship　between　PO4-　and　NH4+　removal　efficiencies　in　the　AAO-BAF　system.　The　NH4+　removal　should　reach　98%　for　over　90%　of　the　PO43-　removal.　When　HRT　of　the　AAO　reactor　was　greater　than　6　h,　and　air/liquid　ratio　of　BAF　was　greater　than　4:1,　the　average　removal　efficiencies　of　COD,　NH4+,　TN　and　PO43-　could　reach　87%,　99%,　80%　and　95%　respectively.　©　All　Rights　Reserved.