The lock washer is a safety washer that prevents the thread from loosening. It consists of two washers. The outside is a radially raised surface, and the inside of the lock washer is a helical tooth surface. When assembling, the inner helical tooth surfaces are opposed to each other, and the outer radial raised surface is in an engaged state with the contact surfaces at both ends. When the connecting piece is vibrated and the bolt tends to loosen, only the inner helical tooth surfaces of the two washers are allowed to face each other. Staggered movement will generate lifting tension, so as to achieve 100% locking effect. Its locking principle conforms to military standards. The anti-loose washer is not only an anti-loosening locking device, but also a high-load locking device that can be used in all strong vibration environments. If the lock washers are used and installed correctly, the nuts and bolts do not need to be retightened, keeping the fasteners safe.