In order to improve Multi-polar magnetic structure's efficiency. Ansoft Maxwell of electromagnetic field finite element software is utilized to study the effect of different polarity arrangement of magnetic seeding element on the magnetic induction intensity of seeding element end and magnetic field distribution in the seeding air gap. As a result of the different electromagnetic coil current direction, magnetic polarity side is different, space structure of magnetic field distribution is also different. The suction metering device of the scope and efficiency is decided by the magnetic field distribution. According to the results of finite element analysis of magnetic field, research on magnetic drum seed-metering device with the design of the program components, and enhance the precision seed metering device performance. Studies have shown that the magnetic induction intensity of seeder in the same polarity arrangement such as NN or SS is lower than in the arrangement of cross with NS, and magnetic field is uniform along the circumference and non- uniform along the axial in the both the arrangement.