Abstract: During flood season, the water level of tailings reservoir often goes up and down abruptly, and the seepage line of tailings dam also changes accordingly, and the dam is in the state of unstable seepage, which has an adverse effect on the anti-sliding stability of the dam.According to flood regulating calculation of tailings reservoir, the change of water level of tailings reservoir in flood season is determined.The seepage stability analysis model of tailings reservoir is established, and the reservoir water level determined by flood regulating calculation is taken as the unstable seepage analysis parameter to carry out the unstable seepage analysis of dam.The results show that during the sudden rise of reservoir water level, the front part of the seepage line rises with the continuous rise of reservoir water level, forming an inverted S-shape; during the sudden drop of reservoir water level, the front part of the infiltration line falls with the continuous drop of reservoir water level, forming an arc shape.Due to the rapid change of reservoir water level and the influence of dam permeability, the rear of the seepage line changes very slowly, not form a stable seepage line within the dam.On this basis, the anti-sliding stability of the dam is analyzed.The results show that the safety coefficient of anti-sliding stability of the dam decreases from 1.474 to 1.465 during the sudden rise of the reservoir water level, which has little influence on the stability of the dam.However, once the stability seepage line is formed at the maximum flood level, the safety coefficient of anti-sliding stability of the dam decreases to 1.357 obviously.The safety coefficient of anti-sliding stability of the dam increases from 1.357 to 1.367 during the sudden drop of reservoir water level, which has little influence on the stability of the dam.However, once the stable seepage line is formed at the normal running water level, the safety coefficient of anti-sliding stability of the dam increases to 1.474 obviously.