Two　main　operating　parameters　(influent　C/N　ratio　and　electric　current　intensity)　were　examined　for　their　impacts　on　the　denitrifying　bacterial　community　structure　in　an　integrated　system　of　three-dimensional　biofilm-electrode　reactor　and　sulfur　autotrophic　denitrification　(3DBER-SAD).　It　was　found　that　genus　beta-proteobacteria　played　a　leading　role　under　different　operating　conditions.　The　influent　C/N　ratio　illustrated　a　great　impact　on　denitrifying　bacteria　diversity.　When　the　C/N　ratio　decreased　from　1.07　to　0.36,　the　Shannon-Wiener　index　and　Simpson　index　increased　from　2.44　to　2.71　and　from　0.89　to　0.92,　respectively,　while　the　proportion　of　heterotrophic　denitrifying　bacteria　Thauera　decreased　from　61.4　to　21.1%,　and　the　sulfur　autotrophic　denitrifying　bacteria　(e.g.,　genus　Sulfuricella　and　Thiobacillus　denitrificans)　increased　from　3.5　to　19.3%.　In　terms　of　the　impact　of　electric　current　intensity,　the　Shannon-Wiener　index　and　Simpson　index　decreased　from　2.71　to　2.63　and　from　0.92　to　0.90,　respectively,　as　the　current　intensity　increased　from　60　to　400　mA.