Abstract: ShenJia Yu tailing dam is a second class of height 138m.At present，the dam structure were changed because the discharging method instead of dry tailings，so the work of seismic dynamical analysis should be carried out.Based on the geologic condition and physics mechanics parameters of soil layers，the geometric model of the central section of the dam was built.Seismic dynamica state of tailing dam was calculated in process of wilson-θ step-by-step integration and equivalence linear.The tailing dam seismic velocity，seismic acceleration，seismic displacement，the max main stress，the max shear stress and strain，and the max interstitial hydraulic pressure and natural frequency of vibration in the dam were got.The research has shown that the tailings dam stability is improved with the dry tailings under the loading EL Centro earthquake wave，it was favorable for operation safety.