Actual domestic sewage was treated by SBR process operating in Anoxic/Oxic pattern. Limited filamentous bulking was induced by low dissolved oxygen at normal temperature, and SVI was maintained 150-220 mL/g. Occurrence of limited filamentous bulking and growth of microorganism were researched, as well as optimization of nitrogen and phosphorus removal. Results showed that filamentous bacteria that led to limited filamentous bulking were H. hydrossis, 0803 type, and M. parcicella, which were the dominant filamentous bacteria by the biggest percentage. It was discovered that during phase of low dissolved oxygen, removal rate of NH4(+) -N decreased significantly, from above 95% to 65%, with obviously less PO4(3-) -P and a little higher COD in effluent. Removal rates of NH4(+) -N and TN were greatly improved to above 95% by new operating pattern of Anaerobic/Oxic/Anoxic: transient inlet --> anaerobic stir (0.75 h) --> aeration (5 h) --> anoxic stir (2.25 h) --> settling, drainage (1 h). So efficient, simultaneous removal of nitrogen and phosphorus was realized in system of low dissolved oxygen limited filamentous bulking.