Flange structure for butt joint of pressure-resistant cabin sections of underwater special equipment and mounting method thereof

The invention discloses a flange structure for butt joint of pressure-resistant cabin sections of underwater special equipment and a mounting method thereof. The flange structure for butt joint of the pressure-resistant cabin sections of the underwater special equipment comprises a large-end butt joint flange and a small-end butt joint flange which are located on the inner sides of the two pressure-resistant cabin sections respectively; a boss extending towards one side of the small-end butt joint flange is arranged on the inner ring side of the large-end butt joint flange, and the boss is arranged on the inner ring side of the small-end butt joint flange in a sleeving mode; a groove is formed in the outer ring side of the small-end butt joint flange, the connecting bolt penetrates through the side wall of the groove and then is in threaded connection with the large-end butt joint flange; and the groove of the small-end butt joint flange is covered with a cover plate used for sealing the opening side of the g