Long period displacement pulse and velocity pulse with large value are often found in near-fault pulse-like ground motions, and the short time pulse energy concentration they bring forth is more likely to cause the liquefaction of slag in tailings dams. Taking a tailings dam project in Inner Mongolia Autonomous Region as an example, a two-dimensional finite element model is established to analyze the dynamic response characteristics of the tailings dam, including liquefaction, permanent deformation, acceleration and dam slope stability, by means of the effective stress method of deformation-pore pressure coupling. In addition, the pulse effect of near-fault ground motions and the influence law of deformation-pore pressure coupling on the isodynamic response of tailings dam liquefaction are investigated by the comparison with the total stress method. The results show that the pore pressure of the dam body increases sharply in a short period of time under the action of pulse-like ground motions, and liquefaction is more likely to occur; whereas that under non-pulse-like ground motions rises slowly throughout the first half of the seismic process. The velocity pulse effect of pulse-like ground motions exacerbates the failure of the while dam structure. Compared with the time history of the safety factor of dam slope stability under non-pulse-like ground motions, which experiences small fluctuations of high frequency, that under pulse-like ground motions undergoes large fluctuations of low frequency, with poor slope stability of the tailings dam.