The dynamic analysis of a concrete gravity dam is a reasonably complex problem. The response of a dam subjected to dynamic loading is combined effect of the interaction among dam, reservoir and foundation systems. The profile of the Koyna dam has been adopted for the study of the investigation. Nonlinear concrete properties have been taken into account through concrete damaged plasticity model to simulate the damage induced in the dam body under real time earthquake motion. The study indicates the tensile damage of the dam structure occurred during the earthquake motion. Parametric studies, varying the height of the reservoir and the foundation modulus values, have been conducted to show the influence of reservoir and foundation material on the dynamic response of concrete gravity dam.