The invention discloses a method and device for treating sanitary sewage by virtue of vertical flow. An impeller flow-guide device is arranged at the bottom of an anoxic reaction pond and rotates under the impact of inflowing flow so as to mix sewage with fillings and produce rotating flow and vertical-ascending flow, and anoxic suspended biological fillings attached with biological membranes circularly move with water flow, so that no dead corner is formed in the anoxic reaction pond, the flow field distribution is relatively ideal, and the volume utilization rate of the reaction pond is high; no stirrer is arranged in the reaction pond, so that energy consumption is avoided, and the lives of the fillings are long; and by utilizing a special water guide pipe structure, the rotating flow in the horizontal direction and ascending (or descending) flow in the vertical direction are formed by the water flow in the aerobic reactor, the aerobic suspended biological fillings attached with biological membranes circularly move with water flow, no dead corner is formed in the aerobic reactor, the relatively ideal flow field distribution is formed, and vertical mixed flow is formed, so that the sedimentation of sludge at the bottom of a reactor can be completely avoided, the reaction efficiency is greatly improved, and the volume utilization rate of the reactor is greatly increased.