Abstract: The sintering desulfurization ash is the waste produced by a semi dry Flue Gas Desulfurization (FGD) system. The desulfurization ash, which consists of some unstable mineral compositions, such as CaSO3 and f-CaO, is difficult to recycle. Considering the demand of low cost cementing material for filling stoping in iron mine, a new filling cementing material is prepared with sintering desulfurization ash and water-quenched slag. It is manufactured by a composite activator, composed of quicklime and sulfate, while the quicklime is the main activator and the sulfate is an auxiliary excitation agent. Firstly, the orthogonal design is adopted and implemented. Then, the range analysis is taken and the optimal ratio can be obtained. Finally, an optimal model of composite activator ratio is established and solved by the regression analysis. In view of the requirements in filling stoping, the optimal proportion is obtained. It shows that, when the adding amount of the sintering desulfurization ash is up to 10 %, the mass ratio of the cementing material to tailing being 1:8 and the concentration (by mass) of backfilling slurry being 68 %, the strength of filling body with the age of 3 days, 7 days, 28 days are higher than that of 32.5R cement in the same conditions, as the cost is much lower.