Heterotrophic　bacterium,　the　strain　JQ1004　exhibiting　simultaneous　nitrification　and　aerobic　denitrification　were　isolated　from　activated　sludge　and　identified　as　Acinetobacter　by　16S　rDNA.　This　study　was　focused　on　the　characteristics　of　nitrogen　removal　under　aerobic　condition　by　Acinetobacter　sp.　JQ1004.　Clearly,　a　significant　decrease　of　ammonium　and　COD　was　observed　by　33h,　with　99.45%　and　92.54%　removal　efficiency　respectively　while　NH4+-N　was　used　as　sole　N-source　and　sodium　succinate　was　used　as　organic　carbon　source.　Besides,　while　the　strain　utilized　NO3--N　as　nitrogen　source,　the　removal　efficiency　of　NO3--N　was　84.42%　and　total　93.11%　of　COD　was　decreased　during　34h　of　incubation.　It　was　interesting　to　note　that　higher　C/N　ratio　was　required　in　the　degradation　of　nitrate　than　ammonium　with　the　same　initial　concentration　under　aerobic　conditions.　Based　on　the　description　by　modified　Compertz　model　for　the　experimental　data,　it　was　found　the　isolate　using　ammonium　as　a　sole　nitrogen　source　showed　higher　rate　of　converting　nitrogen　than　using　nitrate,　with　7.93mg/(L·h)　and　4.08mg/(L·h)　respectively.　Response　surface　methodology　(RSM)　experiments　proved　that　efficient　nitrogen　removal　and　growth　of　strain　JQ1004occurred　with　succinate　as　the　carbon　source,　pH　7.33,　31.80,　and　high　C/N　ratio　of　7.76　and　dissolved　oxygen　(with　shaking　speed　of　154.54r/min).　©　2017,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.