The utility model provides a contact mounting structure of circuit breaker, includes bottom plate, static contact and contact backup pad, static contact fixed mounting in the contact backup pad, the bottom plate on seted up the contact via hole, contact backup pad fixed mounting on the lateral wall of bottom plate and the static contact pass the setting of contact via hole. Seted up at least one backup pad mounting hole in the contact backup pad, still seted up on the bottom plate and correspond the backup pad fixed orifices of being connected with the backup pad mounting hole to be equipped with the internal thread on the inner wall of backup pad mounting hole and/or backup pad fixed orifices, the backup pad mounting hole passes through the screw fastening connection with the backup pad fixed orifices. The utility model provides a simple structure, simple and convenient, the stable contact mounting structure of circuit breaker of connection of assembly.