The utility model discloses an external balanced bridge comprehensive testing device, the power distribution box comprises a box body, body cavity is provided with neutral point resistance switch unit, changes power supply, main control unit, detecting element, the box both sides all are provided with the fan, the box top is provided with the touch liquid crystal display screen, touch liquid crystal display screen one side is provided with the wiring hole. The utility model discloses a set up neutral point resistance switch unit, can make the device adaptation direct current system's of transformer substation various demands, change power supply through setting up, avoided arousing the possibility of device outage because of full station has a power failure, incessant power supply has beenguaranteed to stabilize, through setting up the main control unit, it is fast to make the device have an operational speed, the computational accuracy is high, external interface is abundant, characteristics such as interference immunity is strong, through setting up detecting element, can realize the investigation to direct current system earth fault, through setting up the fan, but the radiating effect of reinforcing means during operation.