In　order　to　avoid　the　discharge　of　nitrite　into　the　receiving　water　body,　the　feasibility　of　using　the　oxidation　reduction　potential　(ORP)　as　control　parameters　for　nitrite　accumulation　in　SBR　denitrification　for　the　treatment　of　leachate　via　anoxic/anaerobic　UASB,　was　investigated.　Experimental　results　show　that　under　the　four　different　initial　NO3--N　concentration　used,　nitrite　accumulation　is　observed　obviously　in　SBR　denitrification.　It　also　concludes　that　the　nitrite　accumulation　rate　is　0.117,　0.136,　0.235　and　0.068/d,　respectively.　In　addition,　two　break　points　of　nitrate　and　nitrite　on　ORP　profile　indicate　that　the　nitrate　reduction　reaction　and　nitrite　reduction　reaction　are　completed,　respectively.　For　the　denitrification,　in　which　nitrite　accumulates　obviously,　nitrate　concentration　is　used　as　the　sole　parameter　of　the　denitrification　rate　(rDN)　is　not　accurate,　and　the　total　oxidized　nitrogen　(NO3--N+NO2--N)　should　be　used,　or　named　as　nominal　rDN.　Furthermore,　it　concludes　that　nitrite　accumulation　is　observed　that　at　five　different　C/N　ratios　conditions,　the　accumulation　of　nitrite　caused　by　nitrite　reduction　rate　is　slower　than　nitrate　reduction　rate,　and　for　the　nitrite　peak　value,　it　should　be　a　rate　of　a　balanced　point　according　to　the　Monod　kinetics　equation　analysis.　The　dosages　of　carbon　source　is　sufficient　for　the　conversion　of　NO3--N　→　NO2--N,　however　it　is　deficient　for　transformation　of　NOx--N　→　N2,　when　n(C)/n(N)　was　2.25:1,　3.75:1,　respectively.