Though　sulfamethoxazole　(SMX)　degradation　at　the　low　or　medium　concentration　(SMX＜　30　mg/L)　has　been　reported　in　the　microbial　fuel　cell　(MFC),　further　exploration　is　still　urgently　required　to　investigate　how　the　high　concentration　of　SMX　affect　the　anode　biofilm　formation.　In　this　study,　the　degradation　mechanism　of　SMX　and　the　response　of　microbial　community　to　SMX　at　different　initial　concentrations　(0,　0.5,　5　and　50　mg/L)　were　investigated　in　MFCs.　The　highest　SMX　removal　efficiency　of　98.4%　was　obtained　in　MFC　(5　mg/L).　SMX　at　optimal　concentration　(5　mg/L)　could　serve　as　substrate　accelerating　the　extracellular　electron　transfer.　However,　high　concentration　of　SMX　(50　mg/L)　conferred　significant　inhibition　on　the　electron　transfer　with　SMX　removal　decline　to　84.4%.　The　16S　rRNA　high-throughput　sequencing　revealed　the　significant　shift　of　the　anode　biofilms　communities　with　different　initial　SMX　concentrations　were　observed　in　MFCs.　Thauera　and　Geobacter　were　the　predominant　genus,　with　relative　abundance　of　31.9%　in　MFC　(50　mg/L　SMX)　and　52.7%　in　MFC　(5　mg/L　SMX).　Methylophilus　exhibited　a　huge　increase　with　the　highest　percentage　of　16.4%　in　MFC　(50　mg/L).　Hence,　the　functional　bacteria　of　Thauera,　Geobacter　and　Methylophilus　endowed　significant　tolerance　to　the　selection　pressure　from　high　concentration　of　SMX　in　MFCs.　Meanwhile,　some　bacteria　including　Ornatilinea,　Dechloromonas　and　Longilinea　exhibited　a　decrease　or　even　disappeared　in　MFCs.　Therefore,　initial　concentrations　of　SMX　played　a　fundamental　role　in　modifying　the　relative　abundance　of　predominant　populations.　This　finding　would　promote　theories　support　for　understanding　the　evolution　of　anode　biofilm　formation　related　to　the　different　initial　concentrations　of　SMX　in　MFCs.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.