Automobile safety belt pretensioner

The invention discloses an automobile safety belt pretensioner. The pretensioner comprises a support (11) and an earthen pipe (19) arranged on the side surface of the support (11), wherein a piston (17) and a gas generator (14) are arranged in the earthen pipe (19); the piston (17) pulls one end of a steel wire rope (7) through an aluminum ring (20); a pull ring (3) arranged at the other end of the steel wire rope (7) is connected with a braid through a lock catch assembly (4); an impressed notch capable of preventing the piston (17) from impact dropping is formed in the tail end of the earthen pipe (19); the stroke of the piston (17) is 50 mm; and a steel ball is arranged at the bell mouth of the piston (17) and forms a one-way revolving self-locking mechanism together with the bell mouth of the piston (17). The automobile safety belt pretensioner has the benefits of capability of automatic tensioning in collision, advanced, compact and reasonable structure, safety and reliability.