The invention discloses a device for treating domestic sewage. The device comprises a programmable control device, a sequencing batch reactor (SBR) pool and a dephosphorization pool, wherein a difference of level exists between the SBR pool and the dephosphorization pool; the SBR pool is positioned above the dephosphorization pool; a decanter, an aerator pipe and an intermittent sewage stirrer are arranged in the SBR pool; the bottom of the SBR pool is provided with a water inlet pipe and a dredge pipe; the aerator pipe is connected with an aerating apparatus; a stirrer is arranged in the dephosphorization pool; the bottom of the dephosphorization pool is provided with a sewage draining exit which is connected with the water inlet of a water pump and a chemical sludge dredge pipe; the water outlet of the water pump is connected with the water inlet pipe at the bottom of the SBR pool; the medicament inlet of the dephosphorization pool is connected with a phosphorus removing agent dosing device; and the water inlet of the dephosphorization pool is connected with the water outlet of the SBR pool. In the device, anaerobic, facultative and aerobic reactions of the sewage are combined in the same pool, so that floor area is saved. Nitrogen and phosphorus are subjected to advanced treatment by combining dephosphorization with biological reactions in the SBR pool, so that the nitrogenand the phosphorus can be removed from the sewage effectively, sewage treatment degree is enhanced and first-class A type discharge standard can be reached finally.