The invention provides a polar region fault treatment method of a hybrid multi-terminal direct current transmission system; when the pole region of an inverter station in the system breaks down, the monopole region of the inverter station is locked, and a polar region locking instruction is sent to a rectifying station and other non-fault inversion stations in the system; after the rectifying station in the system receives the polar region locking instruction, the trigger angle of the fault pole of the rectifying station is moved to a set angle; in the process of phase shifting of the triggerangle, the voltage of an pole port of the fault inverter station is reduced to zero, and the power and the current of the system are interrupted; after the non-fault inverter station in the system receives the polar region locking command, a zero-voltage control strategy is executed; and when the current of an isolation switch corresponding to the fault inverter station is smaller than a set value, the fault inverter station is disconnected. According to the technical scheme, when the polar region of the inverter station breaks down, the fault inverter station can be removed from the system, and the reliability of the hybrid multi-terminal direct current transmission system is improved.