Alkaline residue is an industrial solid waste and pollutant from the process of soda production by ammonia alkali method. Developing its high-value utilizations is of significant economic and environmental benefits. Aimed at developing the application of alkaline residue as the sorbent for wet flue gas desulfurization in coal-fired power plants, the first ever industrial experiment of using the alkaline residue to substitute limestone was carried out on the flue gas desulfurization system of a 1 000 MW coal-fired electricity generation unit designed with a limestone-gypsum wet flue gas desulfurization process. Based on systematical comparison with limestone desulfurization, the performance as well as influences of the alkaline residue for desulfurization was investigated and evaluated. The experiment proves that the alkaline residue is capable to completely replace limestone in the wet flue gas desulfurization system of large-scale coal-fired power unit. Desulfurization of alkaline residue can improve efficiency of flue gas desulfurization and achieve ultra low emission, and has little influence on the quality of by-product gypsum. Alkaline residue replacing limestone as the sorbent can ensure the reliable supply of the sorbent and has the advantages of lower price and electricity consumption and higher flexibility for higher sulfur coals and can achieve good economic benefits. It also achieves using a waste to control pollution and therefore provides significant environmental benefits.