Abstract: The present study investigates and analyses the behavior of a concrete gravity dam during the strong ground horizontal motions due to an earthquake with CADAM. The model in thesis is the structure of Hirakud gravity dam. Hirakud dam across river Mahanadi in eastern India is a composite structure of earth, concrete and masonry. Length of the main dam is 4.80 Km, flanked by 21 km earthen dykes on left and right sides, making a total length of 25.8km. Two concrete spillways of average height 45.75 m and maximum height 60.96 m are located in the two arms of the river. Hirakud dam has been built at Latitude 210-32’ N and Longitude 830-52’E across river Mahanadi at about 15 km upstream of Sambalpur town. This is the first post independence major multipurpose river valley project in India. It hasnot ever shakes under the influence of powerful ground motions in the area. Because of lowness and special firmness of the structure it behaves like a solid body, therefore the structure should be compared with many different earthquake accelerations and then the maximum vibration of the body is considerable. After linear dynamic analysis with CADAM the results show the stresses on the body of the dam are relative to particularity of each earthquake like magnitude, epicenter distance and PGA .The body of dam is modeled two dimensional in CADAM. The procedure of analyses is linear response spectra analysis. The acceleration records of ground motions in the CADAM dynamic response spectra analysis are real records of occurred earthquakes. The other data which are used in CADAM modeling are approximately unreal and exaggerated and they are used for magnifying the influence of earthquake on the dam body.