Abstract: The tailings dam-break is similar to the reservoir dam-break and the outbreak of the mountain debris flow in the project conditions.Using the project analog method, drawing on research results both the reservoir dam-break and the mountain debris flow, with tailings dam-break its own characteristics, according to the case for gradual dam-break, appropriate adjustments to the original model, getting calculation formulas of peak flow, maximum peak flow downstream along the way and flood peak height from the dam site, giving the time formula the maximum peak flow reached.The formulas are applied to practical project.The results provide sufficient data for the dam-break downstream impact analysis, and it is the necessary data for tailings dam design and management.It provides the theoretical basis for site selection of tailings dam.

Key words: Tailings dam, Dam-break, Numerical calculation, Influence analysis