The invention provides a neural point grounding device and a control method thereof. The neural point grounding device comprises an arc suppression coil with one end connected with the neural point and the grounded other end; a resistor unit in parallel connect with the arc suppression coil and used for providing a resistor capable of changing a resistance; a controller for controlling the resistance of the resistor unit and the on-off of the resistor unit circuit. Through the neural point grounding device and the control method thereof provided by the invention, the resistance is maximal wheninputting an adjustable resistor at the primary input, the line metallicity grounding fault and the middle and low resistance grounding fault with large proportion can be judged, the fault current issmall, and the personal safety is guaranteed; for tiny minority of grounding fault with transition resistor as high resistance, the fault line is not distinguished, the adjustable resistor can be automatically adjusted to the minimum, the fault feature is further increased, and an accuracy rate of the fault selection is improved.