The invention discloses a pole-mounted circuit breaker with a built-in isolation switch, and belongs to the technical field of power generation, power transformation or power distribution. A circuit breaker switch, an isolating switch and a transmission mechanism of the isolating switch are arranged in the same sealed box body, the circuit breaker switch comprises an arc extinguishing chamber, anarc extinguishing chamber static end copper guide rod and a contact spring assembly, the isolating switch comprises a moving contact and a static contact, the transmission mechanism comprises a synchronizing shaft, an output crank arm, an insulating pull rod and a rotating assembly, and the whole main loop is loaded in an insulating box. The problems that a common pole-mounted circuit breaker is small in opening distance and cannot serve as a reliable fracture, and an isolation switch and a pole-mounted load switch cannot remove short-circuit faults are solved, rapid mechanical linkage of thecircuit breaker and an isolation knife is achieved, and the condition of achieving the rapid reclosing function is achieved.