The invention relates to the field of magnesium alloy plate stamping preparation, and discloses a hot-pressing forming device and hot-pressing forming method for a magnesium alloy plate, the magnesiumalloy plate prepared through the hot-pressing forming device and the hot-pressing forming method and an application of the magnesium alloy plate. The hot-pressing forming device for the magnesium alloy plate comprises an upper die and a lower die, moreover, the upper die is connected with an upper die plate, the lower die is connected with a lower die plate, moreover, a pre-forming oil cylinder,a discharging block and a female die are arranged on the upper die, a male die, a blank holder and a lower jacking cylinder are arranged on the lower die, the pre-forming oil cylinder drives the discharging block to perpendicularly ascend and descend, the lower jacking cylinder drives the blank holder to perpendicularly ascend and descend, a main cylinder is arranged at the top, and drives the upper die plate to perpendicularly ascend and descend, and then the upper die plate drives the female die to perpendicularly ascend and descend. The product prepared through the hot-pressing forming device and the hot-pressing forming method is good in drawing effect, free of scratches on the surface, free of cracks on a round corner, and capable of being applied to an automobile seat.