The invention relates to an internal circulation fluidized bioreactor used for the sewage treatment, a pool body thereof is internally provided with a fluidized aerobic reaction zone, a settlement collecting area and an anoxic reaction zone, the bottom of the pool body is provided with an aeration device, the top part of the settlement collecting area is provided with a yielding aqueduct, the anoxic reaction zone is internally led with a water inlet pipe, the top part of the anoxic reaction zone is provided with an exhaust pipe, and the bottom of the anoxic reaction zone is provided with a water distribution pipe which communicates with the anoxic reaction zone and the fluidized aerobic reaction zone. The fluidized aerobic reaction zone is internally provided with a vertical partition board which divides the reaction zone into two zones, gaps communicated with the two zones are arranged on the partition board at intervals, and the aeration device is positioned outside the partition board. Compared with the prior art, the pool body is divided into the anoxic reaction area, the fluidized aerobic reaction zone, and the settlement collecting area, a biological reaction, a mud-water separation, and a sludge return flow systems of the sewage are combined organically, the sewage purification effect is good, the partition board divides the position of the original aerobic zone into two positions, so as to cause the aeration range to be small, the oxygen utilization ratio to be improved, and the aeration effect to be greatly increased.