Different applications of permanent magnet DC motors require different performances. Different performances depend on the internal electromagnetic structure parameters of the motor. In the magnetic parameters, different air gap magnetic field distribution shapes are required, such as permanent magnet direct current for pure output drive. Motors require high output power and efficiency. Therefore, the air gap magnetic field distribution in this type of motor should use a flat top-wave that is equal to or slightly larger than 2/3 of the pole pitch, so as to provide as large a magnetic flux as possible, so that the motor has Larger electromagnetic torque. Another example is for a permanent-magnet DC motor with low vibration, low noise, and small spark, which does not require high output power and efficiency. The internal air-gap magnetic field distribution should use a flat-top or sine wave with a pitch less than 1/3. To ensure the suitability of such motors. To obtain different distribution shapes of the air gap magnetic field waveform, not only related to the rational design of the magnet structure shape and the magnetic orientation of the selected magnet, but also related to the magnetization method of the magnet, ie, the magnetization technology design.