The torque multiplier is composed of a circular or planetary gear combined in different combination layers to drive the gear to rotate and output. In the planetary gear system, the torque is input and output through the sun gear. The rotation is driven by the combination of three or four planetary gears and the sun gear. The circumferential gear in the multiplier housing is engaged with the surrounding inner planetary gear, but the direction of rotation is opposite to that of the inner planetary gear. The reaction arm can prevent the shell integrated with the circumferential gear from rotating, and the planetary gear rotates around the sun gear to drive the square head to rotate, thereby outputting torque.