Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in MSW incineration fly ash were decomposed in the process of sulfuration treatment of heavy metals by mixing fly ash with asphalt, sulfur and sodium hydroxide in a heated bi-axial kneader. Complete decomposition of PCDDs/PCDFs was achieved in accordance with their dechlorination when 100 g fly ash (PCDDs/PCDFs content: 14,490 ng/g) was treated with 25 g asphalt, 5.3 g sulfur and 8.0 g sodium hydroxide at 593 K for 1 hour.