Abstract: At present, it is difficult to accurately judge the location of the break and the flow state of water and sand in the simulation analysis of the tailings dam stability and dam break. Combining the stability of tailings dam with dam break simulation, FLAC^3D is used to calculate the stability of tailings dam under the normal water level, flood water level and overtopping water level. Rhino and Fluent are used to establish the tailings pond and downstream fine terrain, the flow state of water and sand in dam break of tailings pond at different times and under different terrain is studied and analyzed. The results show that the buried depth of the phreatic line decreases with the increasing water level of the tailings pond. When the normal water level rises to the flood level, the buried depth of the phreatic line decreases by 5～8 m. When the normal water level rises to the overtopping water level, the phreatic line of the dam crest moves down about 8 m along the slope. The reservoir water level has a significant impact on the stability of the shear zone and tailings dam. From the normal water level to the flood level, the shear zone extends longitudinally to the interior of the dam body and laterally to the dam toe, and the shear strain rate increases to 5.78×10⁻⁵, the stability coefficient of tailings dam decreases from 1.80 to 1.32. The shear zone shortens sharply when reaching the dam crest, and the shear strain rate further increases to 3.32×10⁻⁴, the stability coefficient of tailings dam decreases from 1.32 to 1.18. The flow state of dam break water and sand is obviously affected by the terrain, which is characterized by convergent flow with reduced range and increased velocity in the valley, and the divergent flow with the increased range and reduced velocity in the flat farmland.