The invention discloses an air-assisted electro-coagulation algae water separation device and a using method thereof, and belongs to the technical field of sewage treatment. The device comprises a tower, a main shaft, concentric cylinder electrode plates, a mechanical transmission device, a connecting rod mechanism, a floating ball device, an air distributor, a pulse air feeding device and the like. The device takes even pairs of concentric cylinders as cathode and anode for electro-coagulation which are distributed in a staggering way; the surface area of the electrode plate is large, the electro-coagulation efficiency is high, and the adsorption precipitation of microalgae on the surface of the electrode can be effectively prevented. The flowing direction of the liquid in the tower is opposite to the settlement direction of the microalgae so as to form cross flow to enhance the mass transfer and improve the electro-coagulation efficiency. The floating ball device can keep the moving components such as the main shaft in the tower, the concentric cylindrical electrode plates of the cathode and anode and the like in a floating state so as to reduce the running load of a transmission motor. The device of the invention can realize continuous operation of electro-coagulation and air floatation collection of the microalgae; and the basic structure is easy to amplify and implement so as to meet the requirements of large-scale industrial continuous running.