An automatic wire tying machine (11) mechanism (10) comprising, on a supporting body (12) of the automatic wire tying machine (11), a movable end portion (18) of a hook-shaped guide (16), which is open inwardly to carry a flexible wire (17), to be closed on an abutment element (20) so as to surround the items to be tied； the movable end portion (18) is moved by means of a kinematic system (22) that is activated by a motor (21) and comprises a rack (23) and a linkage (24), which is connected thereto with a first end (25) and to the movable end portion (18) with an opposite second end (26) at a compensation spring (27) that can be compressed after the closure of the movable end portion (18) on the abutment element (20) during a rotation arc of the rack (23) with which it is intended to activate cutting means (28) for cutting the flexible wire (17) that separate a tie (14) thereof to be tied around the items.
