Sulfur dioxide is absorbed together with the absorption solution, thus being removed. The residual dust is carried by "water drop", and the quality is increased. After desulfuration, the liquid falls into the bottom of desulfuration tower and is discharged into collection system regularly after the desulfuration tower is established. After adding a certain amount of liquefied liquid, the circulating pump is re injected into the spray system and the liquid distribution system again, and the desulfurizer is always in a state of circulation. The desulfurized slurry after multiple cycles is discharged into the post-treatment system. Because of the particularity of the design, when the desulfurized flue gas passes through the tower top demister, the liquid drop in the flue gas is separated, and the effect of dedusting and demisting is achieved at the same time