Abstract: The current analysis of the flow field of an electrolytic tank is based on the assumption of a quantitative single flow of gas or metal solvent. To show the flow field changes of the electrolytic tank in the electrolysis process, numerical simulation of the electrochemical 3D time-varying current field for the rare earth analysis tank was studied by ANSYS Fluent software. 3D simulation analysis of electrochemical transients was conducted in a tank for 12 min with the time of adding neodymium praseodymium oxide as the initial time. The simulation result was consistent with the actual production. It is concluded that the main flow mode of the flow field is the upward flow of gas generated in the inner area of the anode, and the flow rate is always at the maximum. The metal solution generated in the cathode area flows downward, whose flow velocity takes second place. The area between the anode and the cathode forms a longitudinal vortex, and the flow velocity is less than the first two. The lateral area of the anode is a flow dead zone with a minimum flow velocity. The crucible collection area tends to be stable overall, and the flow velocity is far smaller than the inner anode and the cathode area. The praseodymium neodymium oxide is consumed up after electrolysis for 10 minutes, and the flow field velocity gradually decreases.