The invention relates to an operating mechanism of a breaker. The operating mechanism of the breaker comprises a shell body which is provided with a handle, a lock catch, a tripping catch, a contact support and a moving contact are arranged in the shell body, the contact support is made of plastics, locating shafts are arranged in the shell body, the contact support and the tripping catch are both arranged on the locating shafts in a sleeved mode, the lock catch is connected with the contact support in an inserting mode, and the moving contact is connected with the contact support in an inserting mode. The operating mechanism of the breaker further comprises a first reset spring used for resetting the contact support, a second reset spring used for resetting the tripping catch and a third reset spring used for resetting the moving contact. By the adoption of the mentioned technical scheme, the operating mechanism of the breaker enables the mounting and demounting of the lock catch, the moving contact, the tripping catch and the contact support to be convenient, and when the contact support is machined, deformation will not be generated. Further, due to the fact that the tripping catch, the contact support and the moving contact are reset through the three reset spring respectively, the service life of the operating mechanism of the breaker is made to be prolonged.