The　performance　of　nitritation　were　investigated　in　continuous　flow　MBR　fed　with　old　landfill　leachate,　the　inhibition　of　substrate,　product　and　toxicant　on　nitritation　process　and　the　inhibition　kinetics　were　analyzed.　The　results　show　that:　the　nitritation　process　was　started　up　in　MBR　which　controlled　the　NH4+-N　concentration　of　inflow　was　(280±20)　mg/L,　the　DO　was　0.5~1.0　mg/L,　pH　was　7.8~8.2　and　temperature　was　(30±1)℃;　and　at　32d,　the　nitrite　accumulation　rate　was　84.27%.　Influent　load　was　increase　gradually　and　improved　the　DO　to　2~3　mg/L　in　the　next　period,　nitritation　process　was　realized　gradually　in　MBR　system　which　the　inflow　was　the　old　landfill　leachate　completely,　the　ρ　(NO2--N)　of　effluent　from　system　was　889　mg/L　and　the　nitrite　accumulation　rate　was　97.23%　at　112d.　The　inhibition　experiments　of　substrate,　product　and　toxicant　showed　that,　the　inhibition　of　toxicant　surpass　substrate　and　product,　when　the　concentration　of　toxicant　(calculated　by　COD)　was　1600.2　mg/L,　the　ammonia　oxidation　rate　declined　by　22.15%,　and　if　inhibition　factor　was　FA　only　in　corresponding　conditions,　ammonia　oxidation　rate　decreased　by　4.74%~6.49%,　and　if　inhibition　factor　was　FNA　only　in　corresponding　conditions,　ammonia　oxidation　rate　decreased　by　14.46%~15.86%.　Haldane　model,　Aiba　model　and　the　revised　toxicant　inhibiting　model　were　adopted　for　nonlinear　fitting　on　the　experimental　data　respectively,　the　correlation　coefficient　R2　were　0.9821,　0.9961　and　0.9924　respectively,　and　the　inhibition　kinetics　models　of　substrate,　product　and　toxicant　were　obtained.　©　2016,　Chinese　Society　for　Environmental　Sciences.　All　right　reserved.