Lime residuals left from water softening process reused as desulferizer in the coal-fired power plants has been reported. The active composition (CaO) is 43.06 %. 98.77% of lime residuals are particles smaller than 45 µm. The dissolution rate of lime residuals is higher than that of limestone. The results show that the reuse of lime residuals shall facilitate the absorbance of SO2 and enhance the efficiency of desulfurization. Additional corrosion of apparatus and pipes, the slurry bubble or overflow has not been observed during the experiment. The water consumption can be largely reduced, and the gypsum matches the reuse standard. Coal ashes and gypsum are concluded for many kinds of applications.