Ultrahigh vacuum sealing gasket, connecting mechanism and ultrahigh vacuum system

The invention relates to the technical field of sealing, and provides a gasket for ultrahigh vacuum sealing, a connecting mechanism and an ultrahigh vacuum system.The gasket for ultrahigh vacuum sealing is used for being arranged between a pair of connecting flanges and comprises a gasket body; the end, close to the gasket body, of the connecting flange is provided with a sealing face, at least one end of the gasket body is provided with a sealing protrusion, the sealing protrusion is suitable for abutting against the sealing face, the sealing protrusion extends in the circumferential direction of the gasket body, and the sealing protrusion and the gasket body form an integrated structure. According to the arrangement, the back face of the knife edge of the all-metal knife edge flange in the prior art can serve as the sealing face, the sealing protrusion abuts against the back face of the knife edge, ultra-vacuum sealing is achieved, when the knife edge structure of the all-metal knife edge flange is damaged,