Abstract：Abstract：Because of weak strength of soft interlayers，it is noted that rock dynamic stability caused by soft interlayers should be calculated and analyzed. However，dynamic stability analyses have been performed based on numerical simulation，but not on analytical algorithm ever before. Even if there are a few analytical methodologies，most of them are mainly used for SH wave propagating in hierarchical layers. Generally speaking，the thickness of the soft interlayer is much smaller than that of its surrounding layers；and it is shorter than the seismic wavelength. So its dynamic response model would be a scattering model rather than a direct transmission model. It is obviously reasonable that the interbedded reflecting waves should be considered. On the basis of this idea，the dynamic response model for the thin soft interlayer is put forward，which is used for a corresponding computational example.
