Abstract: By means of chemical analysis, thermogravimetry (DTA. TG) and XRD analysis, the influence of compound CaOTiO or CT on the formation of anhydrous calcium aluminosulphate (C4A3S¯) was investigated systematically. The result showed that the compound CaOTiO has almost no effect on the secondary dehydration of dehydrate gypsum as one of the raw materials of C4A3S¯. With the increasing dosage of CT, the activation energy in the decomposition reaction of calcium carbonate gradually lower in value to facilitate calcium carbonate decomposition. Furthermore, the initial synthesizing temperature of calciume drops with the amounts of free gypsum and f-CaO decreasing gradually and the synthesized amount of C4A3S¯ increases. All these facilitate CT the gypsum decomposition with temperature rising.