Abstract：The high-step slope stability of inner dump slope in Heidaigou opencast coal mine under the influences of cast blasting is studied by dynamic similarity simulation experiment and digital speckle correlation method. The results indicate that a lot of rocks above seam are broken and cast to inner dump during the course of cast blasting. The blasted settlement is 17 cm；and the size of blasted rock fragment is homogeneous. The stress wave is strongly directional；and the relative motion occurs at contact plane between inner dump slope and seam earth. The horizontal displacement to free face and settlement occur in the slope；and the settlement in inner slope is the largest. The movements of the inner dump slope，relative to bench height，are very small，which would not lead to landslide or damage. Therefore，it is feasible to apply dynamic similarity simulation experiment to study slope deformation.
