A method and device of torque generation based on electromagnetic effect is provided. An electromagnetic torque whose direction is opposite to the motor driving direction is generated in a magnetic field when a motor-drive armature winding is adopted based on the electro-magnetic induction principle. Meanwhile, a reverse electromagnetic torque which is reverse to the armature winding with the same magnitude, is applied on a magnet set and is transmitted to an underactuated system so as to provide required torque for the underactuated system. Advantageously, the provided torque is in direct ratio to speed, difficulty in control is significantly reduced, two-stage electromagnetic variable speed can be achieved, the design of the system is simple and reliable with a concise and clear structure, and the device may be employed in a wide variety of applications.