An annular aeration biological filter sewage low carbon treatment reactor comprises a pool body, a water inlet pipe, an aeration device and a water outlet pipe. The pool body is composed of three annular galleries from inside to outside, the outer annular gallery and the middle annular gallery serve as reaction zones, filler frames are installed in the reaction zones, space is reserved between the filler frames, gaps are reserved between the filler frames and a pool wall, and the inner annular gallery serves as a settling zone. One end of the outer annular gallery is connected with the water inlet pipe, the other end of the outer annular gallery is communicated with a middle ring through the galleries, inlet water of the inner annular gallery comes from overflow of the middle ring, outlet water is connected with the central water outlet pipe, aerobic zones and anoxic zones are arranged in the an outer ring and the middle ring in staggered mode, and aerating devices are arranged below filler frames of the aerobic zones. The reactor is definite in partition, the aerobic zones are high in dissolved oxygen, and denitrification processes of the anoxic zones avoid existence of dissolved oxygen. By means of gathering of microorganisms on fillers, residence time of sludge is long, and the reactor has the advantages of being strong in control of nitrous oxide and other greenhouse gases, not easy to block, simple in structure, good in treatment effect, stable and reliable in operation, low in operating cost and the like.