A torque assisting device, a method and a mammary machine are provided. According to an example, the torque assisting device includes a rotating mechanism, a fixing cylinder and an axially elastic force-applying mechanism. The rotating mechanism is provided with a load. An end surface of the fixing cylinder is provided with a motion trajectory having an inclination angle and the fixing cylinder is connected with the force-applying mechanism. The rotating mechanism is abutted on the motion trajectory at one end thereof and rotates about an axis of rotation along the motion trajectory. The inclination angle of the motion trajectory is set according to a torque generated by the gravity of the load. By setting the motion trajectory with an inclination angle and the fixing cylinder, torque associated with rotation angle of the centre of gravity of the load may be output passively, counteracting the torque generated by the load's gravity.
