The utility model discloses a by-pass switch trigger device for an MMC flexible direct current power transmission submodule. The by-pass switch trigger device comprises an energy storage circuit and a trigger circuit, wherein the energy storage circuit is used for being connected with a power supply, the trigger circuit is used for being connected with a closing coil of a by-pass switch, and the energy storage circuit is connected with the trigger circuit. A switching tube is connected in series with the trigger circuit, a control end of the switching tube is used for being connected with a trigger signal end of a submodule controller through a switching tube driving circuit, a trigger control switch is connected between the control end of the switching tube and the ground, and the state of the trigger control switch is consistent with the state of a main contact of the by-pass switch. By means of the by-pass switch trigger device, the trigger control switch is connected with a control end of the switching tube driving circuit and used for switching off the switching tube after the by-pass switch is switched on, so that a power requirement on the switching tube is reduced, and the size is decreased. The trigger device is integrated in the submodule controller, therefore, malfunction caused by interference of lower-pressure control signals of the switching tube when the lower-pressure control signals of the switching tube are connected through long leads is avoided, and the capacity of resisting interference is improved.