Using gypsum from regular automobile takeout gypsum factory is acceptable. The desulfurization efficiency can reach 85% and those desulfurized saturation gas whose temperature is around 65-70°C will be discharged into the air by chimney after removing small drops by demister. Part of the overflow liquid separated by the gypsum cyclone can be returned to absorbent preparation system or absorption tower for use, moreover, in order to maintain internal tower water balance, about 1.7t/h waste water with 2% gypsum should be discharged. Main chemical reaction of the desulfurization technology is: SO2 of the gas in desulfurization absorption tower firstly absorbed by water of the slurry, react with CaCO3 of the slurry to create CaSO3, CaSO3 oxidized by O2 from income air and create gypsum CaSO4•2H2O finally. Its main chemical equation is: