Abstract: Rapid drawdown of reservoir has a great influence on the seepage, deformation and stability of an earth-rock dam. Under earthquakes, it may pose a new threat to the dam safety. Combined with a 300 m-super high core wall earth-rock dam to be constructed, the unsteady and saturated-unsaturated seepage analysis of the dam under the rapid drawdown of reservoir is carried out and the pore water pressure is acquired. Based on the seepage and static stress field, the seismic response of the dam is analyzed to get the basic dynamic response. Meanwhile, the evaluation of seismic stability and permanent deformation of dam slope are also conducted to evaluate its seismic safety. The results show that rapid drawdown of reservoir mainly affects the distribution of pore water pressure of the core and upstream dam body, causes the large change of static average effective stress field of the upstream region of the dam for the high core wall rockfill dams with good barrier performance core and upstream filter protection. The occasional earthquake will significantly affect the dynamic response and the seismic performance of upstream dam slope, and more attention should be paid to it. The change of water level does not affect the distribution of seepage field of the downstream dam body obviously. Therefore, the rapid drawdown of reservoir has little influence on the seismic safety of downstream dam body.