Abstract: The seepage stability is the important factor which impacts the safety and stability of the tailings dam，and the position of the saturation line directly affects the safety and stability of the tailings dam.Taking the concrete tailings dam for example，and based on the measured data on drilling，the suitable calculation parameter and boundary condition are chosen to build a reasonable calculation model to analyze the seepage situation of the tailings dam when the drainage facility is normal or damaged.The conclusion is that the permeability of the primary dam has a close relationship with the seepage stability of the tailings dam.When the impermeable layer of the primary dam is blocked，the permeability at exit is reduced and the saturation line of the dam rises，and even the water may exude from the dam slope.The seepage scheme with the local horizontal holes can effectively reduce the saturation line and ensure the safety of the dam.

Key words: Tailings dam, Seepage, Saturation line, Drainage seepage