Regarding the seismic calculation model of tunnels, three key issues, i.e., the seismic waves, the finite element region and boundary condition and the finite element size, are analyzed in detail in this paper. The following conclusions are drawn: plain bedrock seismic wave should be used in seismic analysis of tunnels; bottomfixed boundary conditions should be adopted in the calculation model of the seismic analysis; instead of boundaries that have transmission functions after finite truncation, large scale truncation boundaries should be adopted based on SaintVenant's principle in case of infinite boundaries on the side; the finite element size should be determined in accordance with the spectrum of seismic waves.