The utility model discloses a low-voltage breaker which has the function of fast tripping. The utility model is characterized in that at least one side of a contact device is provided with an inner-communicated opening convex edge; the bottom of a rotating shaft which is arranged on a base seat is provided with corresponding bearing element; the bearing element receives the over-voltage current which is overflowed from the opening convex edge of the contact device, and transmits to the contact element to magnify through the rotating shaft so as to fast hit the latch to produce tripping. As the force is earlier than the force which is produced by the partial action of the electromagnet inside the heating system and the electromagnetic system, the middle step is reduced, and the low-voltage breaker can be broken earlier, which reduces the breaking time and greatly increases the breaking capability of the breaker. The utility model discloses a low voltage breaker with a quick tripping function, which is characterized in that a contact device is provided with an opening flange which is internally communicated on at least one side face; a corresponding stress member is arranged at the bottom of a rotating shaft on a base, and is used for accepting excess voltage air streams liberating from the opening flange of the contact device; the excess voltage air streams are transferred to a touching member by the rotating shaft, and are amplified; further, a lock catch is quickly struck to generate tripping. As the force of the stress member is generated earlier than force generated by electromagnetic partial action in a heat energy and electromagnetic system, middle links are reduced. Thus, the low voltage breaker can be broken early, breaking time is reduced, and the breaking capacity of the low voltage breaker is raised.