In this paper, the effects of dominant period and duration of seismic motion on the seismic damage of river levees are numerically investigated. The results show that when the long-period component of the input seismic motion is dominant, not only liquefaction of sandy layers but also damage to clayey soil layers showed extensive seismic damage. In addition, since ground motions for design purposes are often specified by response spectra, the effect of duration is not strictly taken into account. Especially in the case of soft ground with strong elasto-plastic response, it is shown that the effect of duration of seismic motion is significant. Numerical analysis shows that it is important to take into account the seismic characteristics such as period and duration for detailed damage estimation.