Abstract: Under the concept of “waste to waste”, coal-fired fly ash and waste incineration fly ash were used as curing agents to evaluate the curing stability of Cu, Zn, Ni, Cr, Cd, Hg, Pb and As in desulfurization sludge, and to optimize their modification. Sludge and fly ash from three different power plants were selected and screened out by TCLP leaching experiment, and the curing experiment was carried out under the condition of 6% curing agent addition and solid-liquid ratio 1∶3. The results showed that both types of fly ash could significantly reduce the leaching concentration of heavy metals, and the overall curing effect of waste incineration fly ash was better. Characterization showed that the hydration products generated during the curing process could fill pores and improve structural compactness, thereby achieving physical coating and chemical adsorption of heavy metals. After further modification of fly ash by ball milling method and alkali excitation method, the curing rate of various heavy metals can be increased to 85%−95%. The results of BCR step-by-step extraction showed that the heavy metals were significantly transformed from easy migration to stable form after curing, which verified the feasibility of fly ash curing technology in heavy metal curing treatment of desulfurization sludge.