A binding medium clamping mechanism includes a rotatable clamping element configured to clamp a binding medium, a driving element configured to drive the clamping element, a one-way transmission element connected between the driving element and the clamping element, and a rotatable clamping head opening element configured to open the clamping element, wherein in the case that the clamping element rotates in a first rotation direction to a position for waiting to clamp the binding medium, the positions of the clamping element and the clamping head opening element interferes with each other, to open the clamping element, and in the case that the clamping element rotates in a second rotation direction opposite to the first rotation direction, the clamping head opening element is pushed by the clamping element to rotate in the first rotation direction to move out of a moving track of the clamping element.