The electric field distribution was the main factor affecting on the current efficiency of electrolysis cell. So, the electric field distribution of magnesium electrolysis cell was studied to improve the current efficiency by two of main finite element softwares, COMSOL and ANSYS. The electric field distribution and its trends with the electrolyte change from 1.25m to 1.40m were calculated by using the two softwares. Form the results, the characteristics of COMSOL and ANSYS can be obtained. The conclusions of the paper will provided a significant reference for choose the appropriate software in practice process.