Asphalt concrete core wall dams constructed in high seismic regions of western China are mostly built on deep overburden layers. The existence of a deep overburden layer obviously changes the seismic characteristics of the earthquakes in the transmission from the bottom of the overburden layer to the dam body. Factors such as the thickness, soil dynamic characteristics and structure form of the overburden layer are considered to establish a two-dimensional finite element model. Based on the uniform input method, the influence of overburden layer on the dynamic response of asphalt core wall dam was analyzed. The results show that the acceleration amplification factor at the top of the asphalt core wall does not increase gradually with the increase of the thickness of the overburden layer. Because there is a critical point of thickness increase, when the thickness exceeds this point, the acceleration amplification factor starts to decrease. Under the same thickness of the overburden layer, the dynamic shear modulus of the overburden increases with the acceleration amplification factor at the top of asphalt core wall, whereas the acceleration amplification factor first increases and then decreases with the increase of the saturation degree of the overburden layer. The energy dissipation function of soft fine sand in the overburden soil reduces the acceleration amplification factor of the layer top by 31.7%.