Abstract: A study on the dynamic response of a rockfill dam with reinforced concrete facing excited by earthquake by means of nonlinear finite element method was presented in this paper. The stability factor against earthquake was calculated from the static and dynamic stresses along the potential slide surface, thus, the history of stability safty factor for reinforced concrete facing and dam slope were obtained. The design history of earthquake acceleration was determined by modifying the recorded history of seismic station near the dam site, while the modifying factor was depended upon the distance between dam site and effective fault. The design history was divided into time intervals, the iteration was taken within interval and going to next interval. The dynamic nonlinear behaviours were considered not only for rock-fill but also for concrete, and the natural frequency of the structure was changed interval to interval. Thus, the nonlinear functions of this problem were considered more completely than other researchers.