Vacuum degree alarm switch

The invention relates to a vacuum degree alarm switch and belongs to the field of automobile brake. A piece-shaped plug is connected with a locating rod, a gasket is riveted with the locating rod, an upper cover is in modeling connection with the locating rod and the piece-shaped plug, a movable contact spring is riveted with a spring seat gasket, a lower casing is riveted with the upper cover, the outer edge of a membrane is extruded and fixed by a space formed by the lower casing and the upper cover, one end of a spring is connected with the spring seat gasket, the other end of the spring is connected with the adjusting screw, a touch claw is in contact and connection with the movable contact spring, an air inlet is formed in the upper cover, and the air inlet is perpendicular to a venting groove which is arranged in the axial direction in the upper cover in the radial direction. The vacuum degree alarm switch has the advantages of being novel in structure and obviously improving the dustproof and waterproof performance of components on the premise guaranteeing communication between an upper cavity and the atmosphere. Especially, the problem that warm vapor in an engine cabin condensates on contacts in low temperature to enable the vacuum degree alarm switch to be in failure is solved.