To　improve　the　denitrogenation　effect　of　three-dimensional　biofilm-electrode　reactor　(3BER),　3BER-S　coupled　system　of　3BER　and　sulfur　autotrophic　denitrification　technology　has　been　applied　for　nitrate　removal　of　simulated　municipal　wastewater　treatment　plant　(WWTP)　effluentwithlowcarbon-nitrogen　ratio　(C/N).　Results　of　the　comparative　test　between　3BER　and　3BER-S　indicated　that　3BER-S　was　superior　in　TN　removal　efficiency,　pH　buffering　and　nitrite　nitrogen　accumulation.　When　TOC:TN:P　=　10.7:10:1,　C(NO3--N)　=　35±2mg/L　and　pH=7.0~7.5　in　the　influent　of　the　systems,　the　average　total　nitrogen　and　nitrate　removal　efficiency　was　about　85%　and　94%　for　3BER-S,　which　was　15%　and　10%　higher　than　3BER　respectively.　And　the　average　accumulation　of　nitrite　nitrogen　was　3.04mg/L　for　3BER-S,　which　was　2mg/L　lower　than　3BER.　The　quantitative　analysis　of　sulfur　autotrophic　denitrification　process　in　3BER-S　showed　that　the　effective　availability　of　elemental　sulfur　was　about　79.5%,　and　sulfur　autotrophic　denitrification　process　accounted　14.07　percent　of　whole　denitrification　process　which　played　an　important　role　in　buffering　pH　of　the　coupled　system.　Based　on　the　clone　library　of　nitrite　reductase　genes　(nirS)　fragments,　all　the　denitrifying　bacteria　in　3BER-S　system　showed　a　high　similarity　with　Betaproteobacteria,　in　which　Thauera,　Thiobacillusdenitrificans　and　Acidovoraxhavea　accounted　for　61.41%,　3.50%　and　19.30%　respectively.　Therefore　when　the　organic　carbon　source　was　sufficient　relatively　in　influent　of　3BER-S,　the　heterotrophic　denitrification　process　played　the　dominant　role,　as　well　ashydrogenotrophicand　sulfur　autotrophic　denitrification　processes　owe　a　certainproportionin　the　system.　©,　2014,　Chinese　Society　for　Environmental　Sciences.　All　right　reserved.