Abstract: In order to solve the problems of high filling cost and poor consolidation effect of tailings, this paper uses low-quality slag, fly ash and other active materials to prepare filling cement and optimizes the slurry parameters, so as to meet the filling requirements and reduce the filling cost.Firstly, the physical and chemical characteristics of the test materials are analysed, and the cement ratio is determined by orthogonal test and range analysis, and the hydration mechanism is analysed.Then, the influence of cement sand ratio and mass concentration on the strength of the filling body, the fluidity and stability of the slurry are analysed by the slurry ratio test.Finally, the multi-attribute decision-making model is used to optimize the slurry parameters, and the slurry optimization parameters that meet the requirements of the mine are obtained.The research results show that the proportion of low-quality slag composite cement are clinker 8%, desulfurized gypsum 14%, fly ash 10%, slag 68%.The hydration of clinker promotes the hydrolysis of slag and fly ash, and a large amount of gel is generated by hydration.A small amount of ettringite is generated under the action of desulfurized gypsum, and the strength gradually increases with the increase of hydration products; the strength of filling body increases with the increase of slurry concentration and cement sand ratio, and the slump and bleeding rate decrease with the increase of slurry concentration and cement sand ratio; the optimum parameters of the filling slurry are the ratio of cement to sand is 1∶4, and the mass concentration is 70%.Through test verification, the filling material will meet the requirements of the mine.