The wet-based desulfurization gypsum is fed into a φ3×25m high-efficiency rotary dryer through a double-screw feeder and a belt conveyor for drying, and the physical water is taken off. The dryer uses a high-temperature flue gas boiling furnace to provide a heat source, and the dryer exhaust gas is discharged. The high-temperature air bag pulse bag type dust collector discharges the dust after reaching the standard, and the dry desulfurization gypsum (CaSO4·2H2O) of the dryer is sent to the Fahrenheit mill for grinding. After the sieve is separated, it is sent to the boiling calciner and the desulfurization gypsum. After boiling calcination, the two crystal waters are separated into half a crystal water to prepare a mature gypsum powder (CaSO4·1/2H2O), that is, a desulfurized gypsum powder.