To　date,　only　a　few　microbial　community　studies　of　cold　seeps　at　the　South　China　Sea　(SCS)　have　been　reported.　The　cold　seep　dominated　by　tubeworms　was　discovered　at　South　Yungan　East　Ridge　(SYER)　offshore　southwestern　Taiwan　by　miniROV.　The　tubeworms　were　identified　and　proposed　as　Paraescarpia　formosa　sp.　nov.　through　morphological　and　phylogenetic　analyses.　The　endosymbionts　in　the　trunk　of　P.　formosa　analyzed　by　a　16S　rRNA　gene　clone　library　represented　only　one　phylotype,　which　belonged　to　the　family　Sedimenticolaceae　in　Gammaproteobacteria.　In　addition,　the　archaeal　and　bacterial　communities　in　the　habitat　of　tubeworm　P.　formosa　were　investigated　by　using　high-phylogenetic-resolution　full-length　16S　rRNA　gene　amplicon　sequencing.　The　results　showed　that　anerobic　methane-oxidizing　archaea　(ANME)-1b　was　most　abundant　and　ANME-2ab　was　minor　in　a　consortia　of　the　anerobic　oxidation　of　methane　(AOM).　The　known　sulfate-reducing　bacteria　(SRB)　partners　in　AOM　consortia,　such　as　SEEP-SRB1,　-SRB2,　and　-SRB4,　Desulfococcus　and　Desulfobulbus,　occurred　in　a　small　population　(0-5.7%)　at　the　SYER　cold　seep,　and　it　was　suggested　that　ANME-1b　and　ANME-2ab　might　be　coupled　with　multiple　SRB　in　AOM　consortia.　Besides　AOM　consortia,　various　methanogenic　archaea,　including　Bathyarchaeota　(Subgroup-8),　Methanocellales,　Methanomicrobiales,　Methanosarcinales,　Methanofastidiosales　and　Methanomassiliicoccales,　were　identified,　and　sulfur-oxidizing　bacteria　Sulfurovum　and　Sulfurimonas　in　phylum　Epsilonbacteraeota　were　dominant.　This　study　revealed　the　first　investigation　of　microbiota　in　and　around　tubeworm　P.　formosa　discovered　at　the　SYER　cold　seep　offshore　southwestern　Taiwan.　We　could　gain　insights　into　the　chemosynthetic　communities　in　the　deep　sea,　especially　regarding　the　cold　seep　ecosystems　at　the　SCS.