The invention discloses a high-voltage grounding wire clamp comprising a left clamping plate and a right clamping plate which are hinged by a pin shaft and respectively composed of a clamping blade and a clamping handle. The outer side face of one end, far away from the pin shaft hinge position, of each clamping blade is hinged with an extension arm through a hinge pin of which the head part is provided with an end cap, the outer cylindrical surface of the hinge pin is sheathed with a compression spring disposed between the end cap of the hinge pin and the outer side face of the extension arm, and the inner side face of the extension arm is flush with the inner side face of the clamping blade when being forwardly hinged in the extension direction of the clamping blade. The position, at which the extension arm is hinged, on each clamping blade is provided with a limiting slot for keeping the extension arm forwardly extended, the limiting slot is an arc metal sheet, one end of the arc of the metal sheet is fixed on the clamping blade, and the other end of the arc correspondingly is in clamped contact with the outer side face of the extension arm. The high-voltage grounding wire clamp of the invention has the advantages of simple structure, convenient operation, and high success rate of operation.