Arch dams suffer time-varying external loadings and harsh environment that harm their physical properties. With the aging of such dams, damage accumulates and concrete degradation inevitably appears. In this paper, a model is proposed for simulating concrete degradation with aging because of chemo-mechanical damage. The seismic response of an arch dam with aging effects is analyzed using the proposed model. The results show that the damage caused by the aging of arch dams may result in an increase in tensile cantilever stresses during earthquakes. Meanwhile, the dynamic displacement and joint opening also clearly increase in comparison with those without damage. Thus, the seismic safety of arch dams is reduced by aging effects. Archived this way, the dams suffer time-varying external loadings and harsh environments that harm their physical properties. With the aging of such dams, damage accumulates and concrete degradation inevitably appear. In this paper, a model is proposed for simulating concrete degradation with aging because of chemo- The seismic response of an arch dam with aging effects is analyzed using the proposed model. The results show that the damage caused by the aging of arch dams may result in an increase in tensile cantilever stresses stresses during earthquakes. Meanwhile, the dynamic displacement and joint opening also clearly increase in comparison with those without damage. Thus, the seismic safety of arch dams is reduced by aging effects.