Limestone/limestone-gypsum flue gas desulfurization uses limestone or lime as the desulfurization absorbent. Limestone is crushed and ground into powder and mixed with water to form absorption slurry. When limestone is used as absorbent, lime powder is digested and added with water to form absorbent slurry. In the absorption tower, the absorbent slurry is contacted and mixed with the flue gas, and the sulfur dioxide in the flue gas is removed by chemical reaction with the calcium carbonate in the slurry and the blown-in oxidized air. The final reaction product is gypsum.