In　this　study,　enhanced　removal　of　nitrogen　from　real　domestic　wastewater　with　low　organic　carbon　to　nitrogen　ratio　of　2.1-3.6　was　achieved　in　a　sequencing　batch　biofilm　reactor　(SBBR)　with　enriching　anammox　bacteria　in　situ.　The　SBBR　was　inoculated　with　ordinary　nitrification　sludge　and　operated　under　alternative　anaerobic,　aerobic　and　anoxic　patterns.　During　the　start-up　period,　influent　nitrogen　and　carbon　loading　rate　gradually　increased.　According　to　the　quantitative　microbial　analysis,　the　growth　of　ammonium　oxidizing　bacteria　and　anammox　bacteria　were　promoted,　resulting　in　an　increase　from　6.56　x　10(4)　to　1.51　x　10(7)　and　from　1.11　x　10(4)　to　1.69　x　10(6)　gene　copies.mL(-1),　respectively.　During　the　steady　period　(Day　102-205),　nitrogen　removal　efficiency　of　88.2%　was　achieved　with　an　effluent　total　nitrogen　of　6.3　mg　NI-1　for　average　influent　ammonium　of　53.9　+/-　4.0　mg.L-1.　Nitrogen　removal　was　steady　when　temperature　decreased　from　27.0　to　12.8　degrees　C.　Variations　in　nitrogen　compounds　suggested　that　anammox　reaction　could　be　the　main　pathway　for　nitrogen　removal,　according　to　the　results　of　activity　batch　and　continuous　tests.　For　the　high　nitrogen　removal　performance,　biofilm　and　post-anoxic　unit　could　play　important　roles.　Overall,　this　study　provided　an　alternative　method　to　improve　the　removal　of　nitrogen　from　sewage　by　directly　enriching　anammox　bacteria.