The invention belongs to sensor technologies and relates to a mechanical pressure annunciator or a pressure sensor or the like with metal contacts, in particular to a device for preventing arc discharge of the metal contacts. The device comprises copper foil, springs and a film, wherein the copper foil is composed of an upper copper foil body and a lower copper foil body, the film is clamped by the upper copper foil body and the lower copper foil body, the upper copper foil body and the lower copper foil body are welded with each other and are then closely bonded to the film after being welded so as to guarantee the air impermeability of the interior of the film, and the springs are arranged on the two sides of the lower copper foil body in the film. The device is welded to the metal contacts; when the metal contacts make contact with each other, the copper foil bodies in the film make contact with each other and compress the springs, and then a circuit is closed; when the metal contacts are separated from each other, the copper foil bodies in the film are separated under the action of the springs, and because helium is filled into the film, arc discharge will not occur even a current is too large. The device is simple in structure, small in size, capable of effectively preventing arc discharge and especially suitable for the mechanical pressure annunciator or the pressure sensor.