The invention provides a sequencing batch reactor-membrane bioreactor (SBR-MBR) integrated sewage treatment system and a sewage treatment method. The SBR-MBR integrated sewage treatment system comprises a first reaction tank, a second reaction tank, a backflow pump, a liquid level monitoring probe and a programmable logic controller (PLC) control system. Sewage to be purified is conveyed to a first reaction tank through a pipeline by a water inlet pump, and sewage is stirred in the first reaction tank and then flows into the second reaction tank, wherein an aeration device is arranged at the bottom of a membrane assembly, and the aeration device is connected with an air outlet of an air blower. The backflow pump is used for pumping a sludge-water mixed liquid of the second reaction tank into the first reaction tank through a pipeline, so that hydraulic circulation between the aerobic reaction tank and the anoxic reaction tank is realized. A suction pump is connected with the water outlet end of the membrane assembly, separation of water with sludge and microorganisms in the sewage is realized through the membrane assembly, and the separated water is discharged through a water outlet pipeline; and a carbon source adding device and a phosphorus removal agent adding device are used for respectively adding a carbon source and a phosphorus removal agent into the first reaction tankand the second reaction tank through reagent adding pipelines. The whole system is controlled by the PLC control system, so that the automation degree is high.