The invention discloses a activated sludge reaction separation method for sewage by a sponge substrate, which comprises the following steps of: arranging a membrane module in a reaction tank; connecting the membrane module to a sewage pump; arranging an aerator on the lower part of the membrane module; and putting the activated sludge into the reaction tank, wherein the membrane module comprises a frame, a supporting grid and a sponge; filling the sewage into the reaction tank for aeration; switching on the sewage pump to make the sewage pass through the sponge; adsorbing the activated sludge on the sponge to form a sludge layer, converting the sludge layer into an anaerobic layer and an aerobic layer, and closing the sewage inlet of the reaction tank; after discharging the sewage in the reaction tank, switching off the sewage pump, filling the sewage into the reaction tank for aeration, driving the sewage through the aeration to make the sewage pass through the anaerobic layer and the aerobic layer so as to form an A/O area, and circularly running. An activated sludge reaction separation device for the sewage by the sponge substrate comprises the reaction tank; the aerator, the membrane module, a water outlet pipe and a water inlet pipe are arranged inside the reaction tank; the membrane module comprises the frame, the supporting grid and the sponge; the water outlet pipe is communicated with the frame; the sewage pump is arranged on the water outlet pipe; and the aerator is positioned on the lower part of the membrane module.