This study investigates the stability and dynamic safety analysis of surrounding rocks of a deep underground excavation subject to seismic loading. This study firstly selects the appropriate original earthquake time histories and synthesizes the design acceleration time histories which are consistent. This study establishes a numeral model with different rock properties and different overburden depths. The dynamic analysis of underground excavation under different conditions was carried out with the input data. The concept of Factor of Safety (F.S.) based upon MohrCoulomb failure criterion was used in this study. The study shows that: 1) The value of F.S. of surrounding rock decreases due to a rapid increase in deviator stress when getting closer to the excavation region. 2) The value of F.S. has a decreasing trend as the overburden depth increases. 3) The effect of earthquake on the value of F.S. decreases with the increasing of overburden depth.