The invention discloses a device and a method for domestic sewage treatment. The method includes the steps of precipitation digestion, anaerobic reaction, aerobic biological degradation and reprecipitation. The anaerobic reaction performed segmentally includes a hydrolytic acidification segment and two methanogenesis segments, so that different microorganisms give full play to pollutant degradation capabilities in respective suitable environemts, particularly, corresponding spatial environments are provided for different methanogens, and conditions are created for respective advantage growth. In the aerobic biological degradation step, biological membranes are attached to thin-layer water to contact with air sufficiently, and absorption of oxygen in the air is strengthened. During large sewage quantity, the aerobic biological membranes contact with the air and sewage alternately; and during small sewage quantity, the thin-layer water on the surfaces of the biological membranes contacts with the air continuously. Compared with the prior art, the device for domestic sewage treatment has the advantages of optimized spatial arrangement of function units, compact structure, good sewage treatment effect, no energy consumption, avoidance of personnel operation, high process space utilization rate and occupied area saving.