Magnetic coupling is a new transmission mechanism, a pure mechanical product and has no working environment restrictions. It is more suitable for flammable and explosive environment. Because the magnetic coupling is a transmission device that transmits torque through magnetic field, there is no mechanical connection between the motor and the load shaft. When the motor rotates, the copper magnetic disc on the magnetic rotor cuts the magnetic lines of force in the strong magnetic field generated by the permanent magnet rotor which made of rare earth material, so as to generate eddy current in the magnetic disc. And the strong eddy current moves in the relative motion between the magnetic rotor and the permanent magnet rotor. By adjusting the air gap between the rotor and the permanent magnet rotor, the size of the magnetic field is changed to achieve the function of torque transmission and speed regulation.