Spatial distribution of slope mechanical parameters on its collapsing and sliding due to seismic load is studied by applying rock dynamic triaxial shear test and finite difference numerical simulation. The results show that a difference in elevation is evident in response of slope initial collapsing and sliding triggered by seismic dynamic influence, i.e., initial fracturing always originates in the place of slope shoulder. Secondly, critical failure strain of slope body unit decreases with its buried depth, and double factors that critical failure strain decreases and peak ground acceleration increases in slope shoulder result in its initial fracturing. Thirdly, dynamic shear strength of slope body unit decreases with its buried depth, and double factors that dynamic shear strength decreases and peak ground acceleration increases in slope shoulder lead to its initial fracturing. The above results contribute to revealing key controlling factors and dynamic process of slope collapsing and sliding triggered by seismic load.