For the electromagnetic ball active balance system,its working principle was analyzed,the calculation method of the corresponding compensation capacity of steel balls was summarized,the process of calculating the phase of two steel balls from the known unbalance was discussed,the multi ball situation was simplified into two ball situation according to certain rules,and the relationship between the measurement of unevenness and the number and phase of steel balls was obtained.Under the specific rotor diameter,the three-dimensional model of the balance system structure was established.Based on Ansoft Maxwell finite element analysis platform,the influence laws of permanent magnet arrangement mode,diameter,thickness and electromagnetic structure on the balance speed and compensation were studied by using the control variable method.Finally,the structure design was completed.The results show that when the adjacent permanent magnets are alternately arranged with opposite polarity,the diameter of permanent magnets is 6 mm and the thickness of permanent magnets is 4 mm,and the length of electromagnetic structure shell is slightly less than the length of iron core,the balance system can obtain more reasonable speed and maximum compensation.