Ammonia　removal　by　nitrifiers　at　the　extremely　high　salinity　poses　a　great　challenge　for　saline　wastewater　treatment.　Sequencing　batch　reactor　(SBR)　was　conducted　with　a　stepwise　increase　of　salinity　from　10　to　40　gNaCl.L-　1,　while　sequencing　batch　biofilm　reactor　(SBBR)　with　one-step　salinity　enhancement,　their　nitrification　performance,　microbial　structure　and　interaction　were　evaluated.　Both　SBR　and　SBBR　can　achieve　highefficiency　nitrification　(98%　ammonia　removal)　at　40　g-NaCl.L-　1.　However,　SBBR　showed　more　stable　nitrification　performance　than　SBR　at　40　g-NaCl.L-　1　after　a　shorter　adaptation　period　of　4-15　d　compared　to　previous　studies.　High-throughput　sequencing　and　metagenomic　analysis　demonstrated　that　the　abundance　and　capability　of　conventional　ammonia-oxidizing　bacteria　(Nitrosomonas)　were　suppressed　in　SBBR　relative　to　SBR.　Gelidibacter,　Anaerolineales　were　the　predominant　genus　in　SBBR,　which　were　not　found　in　SBR.　NorB　and　nosZ　responsible　for　reducing　NO　to　N2O　and　reducing　N2O　to　N2　respectively　had　s　strong　synergistic　effect　in　SBBR.　This　study　will　provide　a　valuable　reference　for　the　startup　of　nitrification　process　within　a　short　period　of　time　under　the　extremely　high　NaCl　salinity.