A　system　consisting　of　a　two-stage　up-flow　anaerobic　sludge　blanket　(UASB),　an　anoxic/aerobic　(A/O)　reactor　and　a　sequencing　batch　reactor　(SBR),　was　used　to　treat　landfill　leachate.　During　operation,　denitrification　and　methanogenesis　took　place　simultaneously　in　the　first　stage　UASB,　and　the　effluent　chemical　oxygen　demand　(COD)　was　further　removed　in　the　second　stage　UASB.　Then　the　denitrification　of　nitrite　and　nitrate　in　the　returned　sludge　by　using　the　residual　COD　was　accomplished　in　the　A/O　reactor,　and　ammonia　was　removed　via　nitrite　in　it.　Last　but　not　least,　the　residual　ammonia　was　removed　in　SBR　as　well　as　nitrite　and　nitrate　which　were　produced　by　nitrification.　The　results　over　120　d　(60　d　for　phase　I　and　60　d　for　phase　II)　were　as　follows:　when　the　total　nitrogen　(TN)　concentration　of　influent　leachate　was　about　2500　mg/L　and　the　ammonia　nitrogen　concentration　was　about　2000　mg/L,　the　short-cut　nitrification　with　85%-90%　nitrite　accumulation　was　achieved　stably　in　the　A/O　reactor.　The　TN　and　ammonia　nitrogen　removal　efficiencies　of　the　system　were　98%　and　97%,　respectively.　The　residual　ammonia,　nitrite　and　nitrate　produced　during　nitrification　in　the　A/O　reactor　could　be　washed　out　almost　completely　in　SBR.　The　TN　and　ammonia　nitrogen　concentrations　of　final　effluent　were　about　39　mg/L　and　12　mg/L,　respectively.