Abstract: With the electrolysis process of the rare earth molten salt in the electric tank, the cathode shape will undergo electrical corrosion as time goes on, whose cone angle increases continuously at the bottom of the rare earth electric tank, and it has a certain effect on the electrolysis efficiency and the thermal field. With the aid of COMSOL multi physical field coupling software, this paper, using the rare earth cell with dysprosium iron cathode in Vietnam as the research object, simulates the electrolysis characteristics of different cathodes in different electrolysis stages and obtains the curves of the relation between the alpha value of different cathode cones and the maximum current density in the rare earth electrolysis cell. The cathodic electro etching influence of the on the whole process of the electrolytic reaction in the cell is analyzed, providing a reference for the later maintenance of the cell.