The utility model aims to provide a reliable tensioner hook and also a secondary mold opening mechanism with a hook of simple structure. The secondary mold opening mechanism of the proposed tensioner device includes a dynamic mode and a fixed mode, said fixed mode and the dynamic mode cooperate to form a cavity inside, and on the fixed mode there is an injection hole shared with the mold, said dynamic mode includes an action mode and a second action mode, and in said module there is a core rod connected to the second action mode. A hook is mounted on said action mode, a torsion spring is mounted on the hinge axis of the hook, and a table shoulder corresponding to the gripping end of this hook is provided in the second action mode. A limit block is provided below the hook on the fixed mode, which is bonded to the back of the hook.