Response　of　nitrogen　removal　efficiency　and　microbial　interactions　to　organic　pollution　has　been　a　major　issue　in　wastewater　treatment　system.　However,　the　nitrogen　removal　efficiency　and　interactions　among　microbial　community　under　antibiotics　press　is　still　unclear.　Thus,　the　effect　of　sulfamethoxazole　(SMX)　on　nitrogen　removal　and　microbial　responses　of　IVCWs　was　investigated　through　recorded　the　nitrogen　removal　efficiency　before　and　after　adding　SMX　and　random　matrix　theory　(RMT)-based　network　analysis.　Results　showed　that　better　NH4+-N　removal　(＞90%)　after　a　long　period　of　operation　were　achieved　in　IVCWs,　but　NO3--N　was　accumulated.　However,　nitrate　removal　rates　were　significantly　increased　after　long-term　exposure　(60　d)　to　100 μgL-1　SMX　(from　27.35%　to　35.57%)　with　relatively　high　SMX　removal　(53.50%).　Surprisingly,　the　ammonia　nitrogen　removal　rate　(90.07-92.70%)　were　not　significantly　affected　by　SMX　in　IVCWs.　Moreover,　the　bacterial　richness　was　decreased　and　the　bacterial　community　structures　were　altered　by　the　presence　of　SMX,　especially　those　of　nitrogen-transforming　microorganisms.　Molecular　ecological　network　analysis　suggested　that　SMX　had　positive　influences　on　denitrifying　bacteria　interactions　but　reduced　the　network　complexity　and　microbial　interactions　on　whole　molecular　network,　and　among-module　connections　were　weakened　obviously　at　SMX.