The invention relates to an adjustable two-stage sedimentation tank aerobic granular sludge device, which consists of a reaction unit main body, a water feeding system, an aeration system and a sludge sedimentation selection system. Aeration heads of the aeration system are placed in the cavity bottom of the reaction unit main body, the sludge sedimentation selection system consists of a sludge sedimentation area I and a sludge sedimentation area II, the sludge sedimentation area I serves as a sludge reflux area, the lower part of the sludge reflux area is equipped with a tapered sludge collection groove, and the bottom is equipped with a sludge reflux pipe communicated with a sludge reflux port at a water feeding section of the reaction unit main body, an adjustable water outlet is disposed underwater at the end of the sludge sedimentation area I, the sludge sedimentation area II is equipped with an adjustable partition plate to divide the sludge sedimentation area II into two parts, a tapered sludge collection groove is arranged at the lower part of the sludge sedimentation area II and a sludge discharge port is disposed at the bottom, and the upper part at the rear end of the sludge sedimentation area II is provided with a water outlet. The device provided by the invention can realize aerobic sludge granulation, high work efficiency and low cost.