With the increase of concrete age and performance degradation, the dynamic response of concrete dam will change significantly. The heightened gravity dam is also affected by the difference between new and old concrete materials. In order to study the influence of the aging of gravity dam materials and the performance difference of new and old concrete in heightened gravity dams, taking the heightened Danjiangkou gravity dam as an example, the seismic dynamic response analysis is carried out by using the ABAQUS finite element analysis software. The demolition and reconstruction (the new material condition) and the construction according to the heightened height (the old material condition) are compared with the heightened condition, analyzing the responses of heightened gravity dams to the displacement of the crest, the stress at key points, and the plastic damage with the aging of the concrete material properties under seismic dynamics. The results show that with the increase of the aging degree of concrete materials, the dynamic response of the heightened gravity dam is generally better than that of the old materials and inferior to the new materials. The damage of the dam body tends to extend downward to the joint surface of the new and old concrete. The heightened gravity dam has the characteristics of strong adaptability, low damage index and high anti-sliding stability coefficient, which improve the comprehensive characteristics of the dam body. Besides, the weak parts such as the new and old joint surfaces should be reinforced and bonded to give full play to the engineering benefits of heightening the gravity dam.