The resource utilization of calcium-based desulfurization ash has always been an application problem in the industry. In order to verify the desulfurization effect of calcium-based desulfurization ash instead of the original desulfurizer (limestone flour) of limestone-gypsum wet desulfurization system, laboratory and industrial application tests of adding different proportions of calcium-based desulfurization ash to the mixed desulfurization agent are carried out, and the changes of such main process parameters as desulfurization efficiency, SO₂ emission mass concentration, chemical composition of absorption tower slurry and gypsum, as well as the amount of desulfurization sludge are analyzed, and the changes in the production and operation mode of the wet desulfurization system before and after the addition of calcium-based desulfurization ash are compared and analyzed. The results show that when the replacement ratio of calcium-based desulfurization ash is below 50%, the chemical composition of the absorption tower slurry basically does not change, and the system desulfurization efficiency is above 95%; SO₂ emission mass concentration is below 10 mg/Nm³, less than the national emission standard of 35 mg/Nm³, meeting the ultra-low emission requirements of the industry; the chemical composition of gypsum has basically not changed, meeting the social application standards of gypsum; the amount of sludge produced has not increased, and the Cl^- concentration in the absorption tower has increased, however, this can be solved by increasing the amount of wastewater discharged; the operational adjustment of the wet desulfurization system has not changed much, and the operating cost has not increased significantly. The use of calcium-based desulfurization ash instead of limestone flour can provide an economical, friendly and effective way for the comprehensive utilization of dry and semi-dry desulfurization ash.