Abstract: Dynamic response characteristics and destruction of RCC dams under strong earthquake are closely related to physical properties of the compacted layers. In this paper, a gravity dam equivalent model considering the impact of compaction layer under ground motion is established by using the macro equivalent unit, based on mechanical parameters relationship between the roller compacted concrete layers and the concrete bodies, and based on transversely isotropic constitutive model. A comparison between stresses of normal concrete dam and the interlaminar stresses of RCC dam is conducted based on this model. The results show that the equivalent unit method in this paper can well reflect the characteristics of compacted layers impacting on dynamic response of the structure under strong earthquakes, and can improve the computational efficiency. It can conclude that thicker weak interlayer has more effect on interlaminar stresses.