The invention discloses a bipolar shunting method and device of an existing high-voltage DC power transmission system in island running. The method comprises the following steps of S1, setting a DC power threshold value of the DC power transmission system and a switching delay value and a shunting delay value of a DC station control system of the DC power transmission system; S2, detecting whetheran AC contact circuit is broken or not, and entering the step S3 if the AC contact circuit is broken, the bipolar DC total power value of the DC power transmission system is lower than the DC power threshold value set by the step S1 and time reaches the switching delay value set by the step S1; and S3, switching the DC station control system of the DC power transmission system to an emergency DCstation control system from a main DC station control system, and achieving DC bipolar shunting of the DC power transmission system when the time after switching is succeed reaches the shunting delayvalue set by the step S1, wherein the DC power transmission system stops running. By the method, the high-voltage DC power transmission system can trip to bipolar shunting under the island mode from low-power running.