A　novel　combined　partial　nitrification-Anammox　and　partial　denitrification-Anammox　(PnA/PdA)　single　sequencing　batch　biofilm　reactor　(SBBR)　was　established　to　realize　efficient　and　advanced　nitrogen　removal　from　mature　landfill　leachate　with　low　biodegradability.　Nitrogen　removal　rate　and　nitrogen　removal　efficiency　were　increased　to　2.83 ± 0.06　kgN/(m3∙d)　and　98.6 ± 0.2%　by　stepwise　increase　of　dissolved　oxygen　(DO,　from　0.5　to　3.5 mg/L)　and　continuous　carbon　source　feeding.　Comparable　activities　of　ammonia　oxidation　bacteria　and　Anammox　bacteria　were　realized　during　aerobic　period.　More　organic　carbon　was　redirected　from　complete　denitrification　to　partial　denitrification　during　anoxic　period.　The　main　pathway　PnA　jointly　synergized　with　PdA,　which　contributed　to　76.04%　and　19.44%　nitrogen　removal,　respectively.　Nitrosomonas,　Thauera,　and　Kuenenia　dominated　in　floc　sludge　(0.78%,　5.38%,　and　1.14%,　respectively)　and　biofilm　(0.34%,　5.18%,　and　0.98%,　respectively).　Overall,　this　study　provides　new　insight　into　the　high-efficiency　treatment　of　landfill　leachate　at　full-scale　landfill　sites.