The invention discloses a dome valve. The dome valve comprises a valve body, a sealing pad, a ball dome and a cylinder, and further comprises a main sealing ring and a top plate assembly; the top plate assembly comprises a top plate, an annular piston and a piston work doing pipe; the piston work doing pipe drives the main sealing ring to move downwards, finally the main sealing ring is tightly attached to the upper ball face of the ball dome to achieve sealing, and therefore the sealing principle of inflating expanding sealing of an existing expansible sealing ring is changed, a gap between the main sealing ring and the ball dome can be made far larger than the upper limit of the particle size of material particles conveyed by a pneumatic conveying system, material particles left in the dome valve cannot be stuck at the position of the gap between the main sealing ring and the ball dome, and therefore the problem that the sealing ring in the dome valve can be abraded easily is solved from the aspect of the external cause causing abrasion of the existing expansible sealing ring, and the service life of the sealing ring in the dome valve is prolonged.