Abstract: Slag has a significant impact on the mechanical properties of ultrafine tailings,and the addition of slag to ultrafine tailings plays an important role in improving dam stability and improving the operational safety of tailings reservoirs.Based on the theory of sediment erosion,theoretical analysis and indoor experiments were used to deeply analyze the hydraulic erosion resistance of ultrafinegrained tailingsslag mixture under flood top conditions.The study results showed that the erosion resistance of ultrafine tailingsslag mixture (hereinafter referred to as "mixture") under the condition of different slag content is nonlinear under the influence of hydraulic action.With the gradual increase of slag content in the mixture,the erosion rate shows a change mode of first decreasing and then increasing,of which the erosion rate of the mixture is the smallest when the slag content is 40%,that is,the erosion resistance of the mixture is the strongest at this moment.The reduction of the cohesion of the mixture has a greater impact on its erosion resistance,and the influence of the change of the internal friction angle on its erosion resistance is relatively small.The above analysis results has certain reference significance for further study of the impact of hydraulic erosion of tailings dams.