The invention relates to an improved circuit breaker. The improved circuit breaker comprises a shell, an arc-control device, a movable contact, a static contact, a buckling piece mechanism, a control mechanism, a movable contact energy storage partial pressure piece and an abrupt jumping structure. The movable contact energy storage partial pressure piece is arranged between the movable contact and a movable contact frame, and the movable contact is made attached to the movable contact frame by partial pressure of the movable contact energy storage partial pressure piece; the movable contact and the movable contact frame which integrally rotate are made to rotate relative to each other by the abrupt jumping structure so that acting force applied to the movable contact and the movable contact frame can be relieved after deformation and energy storage of the movable contact energy storage partial pressure piece, the movable contact quickly rotates towards the static contact through energy instantly released by the movable contact energy storage partial pressure piece to achieve abrupt jumping switch-on. The improved circuit breaker is reasonable in structure and has the abrupt jumping function, and the service life of the improved circuit breaker is prolonged.