The secondary opening mechanism of the chain tensioner with stretching in this way includes a dynamic mode and a fixed mode I,. The fixed mode I and dynamic mode I are bonded internally to form a cavity, and injection holes 11 are provided on the fixed mode I that are shared with the cavity, and the movable mode includes a dynamic mode 2 and a second dynamic mode 21. a core 5 connected to the second movable mode 21 is provided. a stretching hook 3 is attached to the first movable mode 2, and a stretching hook 3 is attached to the first movable mode 2. the wire tensioner is mounted on the hinge axis of the hook 3 with torsion spring 31, and a table shoulder corresponding to the hook end of this hook 3 is machined on the second motion mode 21. A limit block 13 is provided below the hook 3 of the fixed mode I. The limit block 13 and the back of the hook 3 are bonded.