The　feasibility　of　using　a　single　sequencing　batch　reactor　to　remove　nitrogen　from　medium-age　landfill　leachate　was　examined,　and　an　anaerobic/aerobic/anoxic　process　in　a　SBR　without　extra　carbon　source　addition　was　presented.　Dissolved　organic　matter　could　be　taken　up　partially　and　stored　as　polyhydroxyalkanoates　(PHAs)　in　the　anaerobic　stage　by　the　microorganisms　operated　in　the　anaerobic/aerobic/anoxic　process,　with　glycogen　consumption.　In　the　aerobic　stage,　ammonia　was　oxidized　and　accompanied　by　loss　of　tatal　nitrogen　(TN)　via　simultaneous　nitrification　and　denitrification.　The　stored　PHAs　and　glycogen,　remaining　at　the　end　of　aerobic　stage　could　provide　carbon　source　for　anoxic　denitrification.　In　the　stable　phase,　the　effluent　COD,　NH+4-N,　and　TN　were　525-943　mgL-1,　1.2-4.2　mgL-1　and　18.9-38.9　mgL-1　respectively　when　the　influent　COD,　NH+4-N,　and　TN　were　6430-9372　mgL-1,　1025.6-1327　mgL-1　and　1345.7-1853.9　mgL-1,　respectively.　Nitrogen　removal　from　medium-age　landfill　leachate　could　be　realized　via　the　anaerobic/aerobic/anoxic　process　in　a　SBR　with　the　effluent　of　TN　less　than　40　mgL-1.　Almost　1/3　of　reduced　TN　was　removed　via　SND,　while　2/3　of　reduced　TN　was　removed　via　post-anoxic　denitrification.　©　All　Rights　Reserved.