Simultaneously partial nitrification, anammox and denitrification (SNAD) process was used for treating domestic sewage in a membrane bioreactor (MBR). Domestic sewage was gradually pumped into the system, removal trend of the pollutants were evaluated via the changing of operational HRT and air flow. The nitrogen removal pathway was analyzed via the mass balance analyze studying, and microbial characteristics via clone-sequencing detection. Results suggested that a simultaneous removal of C, N and SS was achieved in the system, with the nitrogen removal rate to 0.65 kg/(m³d), effluent ammonia below 10 mg/L; COD removal efficiency to 87%, effluent COD below 50 mg/L; turbidity removal to 99%, effluent turbidity below 1 NTU, and SS below 10 mg/L, which met the demand of the first grade A standards of Urban Sewage Disposal Plant Contamination Integrated Discharge Standard (GB18918-2002). Denitrification contributed to 12% nitrogen removal while (completely autotrophic nitrogen removal over nitrite, CANON) contributed to 88%, and AOB, anammox and denitrifiers coexisted in the reactor.