For the problem that the seepage force should be considered in the static and dynamic calculation of the concrete connecting section and the homogeneous loam section of a reservoir dam, a method for calculating the seepage force is proposed. A new Fortran subroutine was developed in this study to be implemented into the commercial finite element software MSC. Marc, and the whole seismic response process of the dam was simulated and analyzed. The calculation results show that, under the design earthquake with a 10% exceeding probability in 50 years, the absolute horizontal acceleration response extremum of the dam body is 5.0 m/s²and the maximum amplification factor is 7.70. The maximum permanent deformation under vertical earthquake is mainly concentrated at the maximum cross section near the top of the dam and the earthquake subsidence is about 0.06% of the dam height. The maximum ground motion acceleration and the dynamic displacement response is located at the local of the dam crest. It can be concluded that there is an obvious “whiplash effect” on the dam crest where seismic strengthening should be carried out. The design and filling standard of each district is reasonable as well as the dam filling scheme, and the seismic safety of the dam is good.