The invention discloses a self force augmentation type bidirectional wrench and an operating method thereof. The self force augmentation type bidirectional wrench comprises a handle, a force-augmentation reversing part, a reversing switch, a shifting lever and a sleeve. The force-augmentation reversing part comprises an input shaft, an intermediate shaft, a reversing shaft, an output shaft, an input gear, a transmission gear, a forward gear, a reverse gear, an output gear, a spring and a steel ball. The output gear can be selected to be engaged with the forward gear or the reverse gear through the reversing switch so that the output shaft and the sleeve can rotate in the same direction as the handle or rotate in the direction opposite to the rotating direction of the handle, and the force moment of the handle can be amplified through two-stage gear transmission. The self force augmentation type bidirectional wrench is simple in structure, convenient to operate, capable of screwing and unscrewing screws in two directions, and capable of saving strength.