In this research, the dynamic behavior of the rock foundation of the Moshampa Dam under seismic loads and hydrostatic pressure of water behind the dam has been studied and modeled. The Moshampa Dam is an earth dam type and was constructed in the Ghezel Ozan River basin near the village of Moshampa in Zanjan province. After building the dam model and assigning material properties to the model, applying seismic loading to the dam in the absence and presence of hydrostatic pressure of water on the dam, and defining the boundary conditions governing the problem, the model has been analyzed using ABAQUS software. In order to dynamically analyze the dam, an explicit method that is specific to the dynamic analysis of large models with short dynamic time responses such as earthquakes has been used. The results obtained show that a high stress concentration is applied to the left flank of the dam, which could be due to the heterogeneous topography of the area, but due to the high resistance of the left support rock of the dam in the tuff layer, no failure occurs in this area. While numerical analysis of the model has shown signs of yielding and failure of the tuff rock in the right abutment of the dam.