Due to the factors such as hard grinding, low activity and volume expansion of steel slag, it has not been fully utilized at present.In order to improve the utilization rate of steel slag, taking the full fine tailings of an iron ore as the aggregate, utilize the steel slag, slag, desulfurization gypsum and other solid waste resources around the mine to develop new low-cost filling cementitious materials, and further optimize the ratio.Firstly, the physicochemical analysis of the test material is carried out.On this basis, the cementitious material ratio test and the ratio optimization test are carried out.Determining the ratio of filling cementitious materials.Secondly, the backfill mortar strength test and slurry stability test are carried out.To analyze the influence law of strength, bleeding rate and stratification.Finally, a quadratic polynomial stepwise regression analysis is performed, and taking the filling cost as the optimization goal to establish the optimal function relation of slurry ratio.The optimal proportion of fine tailings aggregate steel slag based composite filling cementitious material is obtained as follows steel slag 40%, slag 50%, desulfurization gypsum 10%.When the slurry concentration is 64% and the mortar ratio is 1∶5, it’s cement strength is much higher than PO.42.5 cement.The cost is about 35% lower than PO.42.5 cement.The research results can explore a new way for the green and clean production of metallurgical mines.