The invention discloses an electrolysis tank used to prepare rare earth metal and alloy thereof. The electrolysis tank comprises an electrolysis tank body, an anode and a cathode arranged in the electrolysis tank body; the anode is composed of two or more groups of anode units, and the cathode is composed of two or more groups of cathode units; and the anode units and the cathode units are alternatively arranged. By using the technical scheme, because the anode units and the cathode units are alternatively arranged in a parallel way, the electrolysis tank is small in cathodic and anodic current density, especially smaller in cathodic current density, and energy consumption of the electrolysis tank is reduced. Additionally, the tank type is simple in structure, and the electrolysis capacity of the electrolysis tank is easy to amplify. Compared with the prior art, the electrolysis tank has no center layout characteristic, and the cathode units and the anode units are alternatively arranged in a parallel way, so that the tank type is easy for scaling up. The electrolysis capacity of the electrolysis tank can be expanded to tens of thousands of ampere even hundreds of thousands of ampere.