In　order　to　find　out　the　reason　of　the　filamentous　sludge　bulking　in　salt-tolerant　sludge　during　saline　wastewater　treatment,　a　lab-scale　nutrient　removal　activated　sludge　system,　based　on　the　modified　MUCT　configuration,　was　used　to　identify　the　occurrence　process　of　filamentous　sludge　bulking.　The　sludge　was　acclimated　for　a　long　period　at　10　g·L-1　salinity　in　the　MUCT　process　and　was　observed　to　have　plenty　of　filamentous　organisms　under　low　dissolved　oxygen　concentration　condition.　Different　operation　strategies　were　used　to　control　the　filamentous　sludge　bulking.　The　pollutants　removal　efficiencies　during　each　control　periods　were　compared　as　well.　The　results　indicated　that　filamentous　sludge　bulking　in　salt-tolerant　sludge　occurred　at　a　low　DO　concentration.　Increased　salinity　inhibited　sludge　bulking　quickly　and　efficiently.　Limited　filamentous　sludge　bulking　could　be　maintained　for　a　long　time　when　ρ(DO2)　was　controlled　at　1.0　mg·L-1　and　ρ(DO1)　was　controlled　at　2.0　mg·L-1.　The　value　of　sludge　volume　index　(SVI)　varied　between　190　ml·g-1　and　210　ml·g-1.　During　this　period,　the　effluent　turbidity　decreased　significantly　due　to　the　filtering　effect　of　filamentous　bacteria.　It　could　be　an　option　to　solve　the　turbidity　problem　of　saline　wastewater　treatment.　©　All　Rights　Reserved.