Layered slopes are very common in nature, the study of its dynamic response is of great significance to the evaluation of slope stability. In order to simulate the propagation process of elastic waves in layered foundation, the viscous-elastic artificial boundary model of layered foundation is established firstly, and then the equivalent load calculation formula considering the primary reflection of medium interface is derived according to the wave dynamics theory, and the accuracy of the input method is verified by a two-layer foundation example. For layered slopes, the ground motion model proposed in this paper and a conventional input method are used to study the dynamic response law of the foundation. The results show that according to the two-layer foundation example, the proposed ground motion model can better meet the accuracy requirements of the seismic engineering. Compared with the conventional method, the cumulative effect of plastic strain energy of the proposed method is more evident, and its dynamic safety factor is relatively small in the analysis of slope dynamics.