High　inorganic　salts　inevitably　impose　a　toxic　impact　on　biological　treatment　processes.　In　this　study,　the　effect　of　salinity　on　the　performance　and　microbial　community　structures　of　partial-denitrification　(PD)　was　firstly　investigated.　Results　showed　the　denitrifying　activities　of　non-domesticated　PD　sludge　were　completely　inhibited　under　a　temporary　high　salinity　(＞=　1.5　wt%).　However,　after　domestication,　denitrifying　activities　maintained　above　50%　of　the　maximum　with　salinity　build-up　step-by-step　from　0.0　wt　%　to　3.0　wt%.　High　nitrite　production　was　stably　achieved　during　120　days　with　nitrate-to-nitrite　transformation　ratio　around　90%.　Further　investigation　showed　extracellular　polymeric　substances　content　of　PD　sludge　increased　from　184.59　mg　gVSS(-1)　to　560.64　mg　gVSS(-1),　accompanied　by　the　elevation　of　average　particle　size.　This　occurred　against　high　salinity　as　a　protective　response　of　PD　bacteria.　Moreover,　Thauera,　the　functional　bacteria　of　PD　system,　was　still　dominant　with　the　relative　abundance　increasing　to　8336%　(3.0　wt%)　from　51.33%　(0.0　wt%).　(C)　2018　Elsevier　Ltd.　All　rights　reserved.