Pressurization and holding device of underground vulcanizing appliance, and method for pressurization, pressure adjustment and pressure holding of same

The invention relates to a pressurization and holding device of an underground vulcanizing appliance, and a method for pressurization, pressure adjustment and pressure holding of the same. A current underground vulcanizing appliance is not convenient to realize pressure adjustment and pressure holding. For this reason, the pressurization holding and holding device of the underground vulcanizing appliance comprises a pressure packet, a water inlet pipe, a water inlet valve, a water return pipe, a water return valve, a pressure meter, a second water inlet valve, a front valve, a rear valve and astair piston pressure adjustment mechanism, wherein the second water inlet valve is disposed at the water inlet pipe between the water inlet valve and the water return pipe; the stair piston pressureadjustment mechanism comprises a shell and a stair piston rod; and the stair piston rod comprises a coarse cylinder body and a fine cylinder body, the area ratio of cross sections of the two bodies is equal to 4:1.8, the stai