In　this　study,　the　microbial　community　structure　was　assessed　in　an　anaerobic　ammonium　oxidation-upflow　anaerobic　sludge　blanket　(ANAMMOX-UASB)　reactor　treating　high-strength　wastewater　(approximately　700　mg　N　L-1　in　total　nitrogen)　by　employing　Illumina　high-throughput　sequencing　analysis.　The　reactor　was　started　up　and　reached　a　steady　state　in　26　days　by　seeding　mature　ANAMMOX　granules,　and　a　high　nitrogen　removal　rate　(NRR)　of　2.96　kg　N　m(-3)　day(-1)　was　obtained　at　13.2　similar　to　17.6　A　degrees　C.　Results　revealed　that　the　abundance　of　ANAMMOX　bacteria　increased　during　the　operation,　though　it　occupied　a　low　proportion　in　the　system.　The　phylum　Planctomycetes　was　only　8.39　%　on　day　148　and　Candidatus　Brocadia　was　identified　as　the　dominant　ANAMMOX　species　with　a　percentage　of　2.70　%.　The　phylum　of　Chloroflexi,　Bacteroidetes,　and　Proteobacteria　constituted　a　percentage　up　to　70　%　in　the　community,　of　which　the　Chloroflexi　and　Bacteroidetes　were　likely　to　be　related　to　the　sludge　granulation.　In　addition,　it　was　found　that　heterotrophic　denitrifying　bacteria　of　Denitratisoma　belonging　to　Proteobacteria　phylum　occupied　a　large　proportion　(22.1　similar　to　23.58　%),　which　was　likely　caused　by　the　bacteria　lysis　and　decay　with　the　internal　carbon　source　production.　The　SEM　images　also　showed　that　plenty　of　other　microorganisms　existed　in　the　ANAMMOX-UASB　reactor.