Since　denitrification　of　landfill　leachate　was　a　challenging　problem,　this　study　modified　SBR　to　improve　the　efficiency　of　nitrogen　removal.　The　effects　of　several　operation　parameters　were　investigated,　including　operation　mode,　dissolved　oxygen,　over　aeration,　and　carbon　nitrogen　ratio　of　the　leachate.　The　results　demonstrated　that　the　modified　SBR　could　reduce　the　COD,　ammonia-nitrogen,　and　TKN　of　the　leachate　from　about　4000　mg/L,　1000　mg/L,　and　1100　mg/L　to　less　than　500　mg/L,　5　mg/L　and　40　mg/L,　respectively,　without　extra　carbon　source,　meaning　that　the　removal　rates　could　reach　up　to　85%,　99%,　and　95%,　respectively.　Besides,　it　was　found　that　the　PHA　content　in　denitrifying　bacteria　was　the　key　factor　affecting　the　denitrification　efficiency.　Nitrogen　removal　efficiency　would　be　improved　by　high　dissolved　oxygen,　anaerobic　mixing　before　aeration　and　less　over　aeration.　Additionally,　the　advanced　denitrification　would　be　achieved　if　the　leachate　carbon　nitrogen　ratio　was　more　than　four.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.