Abstract: To solve the problems of environmental pollution caused by blast furnace slag and desulfurizationsintering flue gas (FGD) ash, a composite cementitious material was prepared using steel slag, sintering FGD ash and cement clinker. The results show that with the amount of sintering FGD ash increasing, the strength of the cementitious material increases firstly and then decreases. When the oxidation temperature of sintering FGD ash is 550℃, the oxidation time is 30 min and the added amount is 5%, the cementitious material achieves excellent reaction performance. The strength of the cementitious material can meet the requirement of 52.5R cement strength in Chinese IndustrialStandards GB 1344——1999.