The invention relates to a giant tire mounting mechanism; the top of a fixed disk is provided with 3-6 hoisting rings, the bottom surface thereof is a plane and is provided with 6-9 radial pawl telescopic chutes, a slide block at the top end of a tire gripping pawl is clamped in the telescopic chute. A rotating chuck is hung below the fixed disk, a gyro shaft is rotatablely and vertically connected with the center of the rotating chuck which is provided with spiral flutes corresponding to the tire gripping pawls, and every pawl extends out the spiral flutes. The rotating chuck is hung at the outer margin of the fixed disk along the top end of a connecting rod with vertical periphery. A rotary power device is connected with the outer margin of the rotating chuck, a guide centering rod of aguide centering device at the top of the fixed disk passes downwards through the center hole of the fixed disk, the gyro shaft and the rotating chuck and is centered with a center mechanism of a vulcanizing machine, the rotary power device drives the rotating chuck to rotate, the spiral flute compresses the pawl to contract, the mechanism moves downwards, the pawl extends into a tire bead, the rotating chuck rotates reversely and the pawl supports the tire bead, in this way, the tire and the mechanism can be dismounted together. The mechanism is applicable to the assembly and disassembly of giant tires, and has simple structure and easy operation.