The invention relates to a dual-sealing flange, which comprises a night-side flange and a sunny-side flange. A groove is formed in the center of one end face of the night-side flange. A lug boss matched with the groove is formed in the center of one end face of the sunny-side flange. The flange also comprises a graphite spiral wound gasket arranged in the groove and a C-shaped metal sealing ring. A trough for accommodating the C-shaped metal sealing ring is reserved around the groove in the end face of the night-side flange. An air inlet through hole and an air outlet through hole are also symmetrically reserved between the groove and the trough in the end face of the night-side flange, and are communicated with the groove through a protective air channel respectively. The dual-sealing flange can run stably and safely in an ultrahigh-temperature highly-corrosive environment, has a good sealing effect, and has the advantage of convenience for assembly and disassembly, a good using condition is created for a sealing part, and the service life of the sealing part is prolonged.