NOVELTY - A membrane bioreactor comprises microorganism reactor (1), membrane filter (2), water pump, blast blower (6), aeration disc (5), pure water tank (7), connection pipelines and valve. The microorganism reactor (1) comprises microorganism reaction tank(s) including microorganism capable of decomposing sewage and microorganism carrier for growing and breeding microorganism. The aeration disc is arranged on outer side of microorganism reactor and comprises sewage groove for containing water from microorganism reaction tank and cylindrical filtering core(s) arranged in sewage groove.    USE - Membrane bioreactor.    ADVANTAGE - The bioreactor has prolonged service life, avoids washing problem of membrane filter by operators and has improved water producing efficiency. The membrane filter does not easily polluted and blocked.    DETAILED DESCRIPTION - Membrane bioreactor comprises microorganism reactor (1), membrane filter (2), water pump, blast blower (6), aeration disc (5), pure water tank (7), connection pipelines and valve. The microorganism reactor (1) comprises microorganism reaction tank(s) including microorganism capable of decomposing sewage and microorganism carrier for growing and breeding microorganism. The aeration disc is arranged on outer side of microorganism reactor and comprises sewage groove for containing water from microorganism reaction tank and cylindrical filtering core(s) arranged in sewage groove. The pure water tank is connected with inner core of cylindrical filtering core and is used for containing water filtered by cylindrical filtering core. An INDEPENDENT CLAIM is included for a sewage purifying method using the membrane bioreactor which comprises pumping sewage into membrane bioreactor and staring blast blower to aerate microorganism reaction tank through aeration disc, and flowing sewage decomposed by microorganism of membrane bioreactor into sewage groove of membrane filter; and flowing sewage in sewage groove into inner core of cylindrical core through filtering of cylindrical core and pumping water into pure water tank through water pump to obtain pure water, and reflowing pure water in pure water tank to inner core of cylindrical filtering core to backwashing sewage intercepted by cylindrical filtering core at interval of the pre-set time.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram illustrating a membrane bioreactor.    Microorganism reactor (1)    Membrane filter (2)    Aeration disc (5)    Blast blower (6)    Pure water tank (7)