The utility model provides a housing frame for an operating mechanism of a circuit breaker, which belongs to the technical field of low-voltage apparatus. The housing frame comprises a left side plate, a right side plate, and at least one connecting shaft used for coupling the left and the right side plates, and is characterized in that at least a pair of stiffening plates is arranged on the inside walls of the left and the right side plates in a position corresponding to the installation site of the connecting shaft. The housing frame has the advantages that impact force transmitted by the connecting shaft can be dispersed; the stress bearing points of the side plates are improved; the deformation and the damage caused by excessive local stress are prevent; and the service life of the side plates is prolonged.