The invention relates to an improved circuit breaker, comprising a casing, a circuit protection actuating mechanism, a traveling contact, a stationary contact, an arc extinguisher and a disengaging mechanism, wherein the circuit protection actuating mechanism is positioned in the casing; the traveling contact is matched with the stationary contact; the disengaging mechanism comprises a disengagingrotor and a drive component to drive the disengaging rotor to rotate, and the traveling contact is arranged on the disengaging rotor; a buckling mechanism is arranged on the disengaging rotor; the drive component cooperates with the buckling mechanism to control the buckling mechanism to buckle or disengage; and the circuit protection actuating mechanism cooperates with the buckling mechanism todrive the buckling mechanism to disengage. The design of the buckling mechanism in the invention separates the disengaging force from the contact pressure, and therefore, no matter how high the contact pressure is, the disengaging force can not increase all along, so that the pressure between the contacts can meet the requirements for the circuit breaker in a circuit environment with different current magnitudes; the disengaging force of the disengaging mechanism can not change, the sensitivity of the circuit breaker can not be affected, and the circuit breaker has a wider universality; and the whole circuit breaker has the advantages of convenient installation and simple structure.