Abstract: With the increase of tailings dam height, the groundwater seepage field will change. When the actual hydraulic gradient at the tailings dam is greater than the critical hydraulic gradient, the tailings dam will produce seepage deformation or instability damage. In order to predict the seepage stability of a phosphogypsum tailings dam, the seepage coefficient was determined by using the groundwater level gauge to resume testing, and the hydraulic gradient were calculated. At the same time, the SEEP/W module of Geo-studio was used to analyze the seepage stability of the phosphorus gypsum accumulation dam under different conditions. According calculation and analysis results, it was found that when the accumulation dam was in 945m altitude, in the absence of beach and 100m dry beach, the actual hydraulic gradient were 0.784 and 0.583. When the accumulation dam was in 960m altitude and in the absence of beach, the actual hydraulic gradient were 0.692. In the above two cases, the altitude of the seepage point of the accumulation dam was higher than the initial dam, the accumulation dam would appear the deformation of the flow soil, the dam was unstable state. When the accumulation dam was in 960m altitude and 100m dry beach, there was no seepage point on the accumulation dam, and the accumulation dam was in the stable state. The results of the research will provide the technical basis for the safe operation and maintenance management of the tailings dam, and will provide reference for the seepage stability of the same tailings dam.