The ground layer is saturated with soft clay and sand in tunnel of Yangtze River-crossing project，which will easily lead to the phenomenon of liquefaction or earthquake-induced settlement under 7 degree earthquake. Therefore，seismic stability analysis of the whole structure-soil system is essential for us to adopting corresponding measures. According to the data of soil dynamic test，it compute the seismic response of the tunnel by finite element method based on effective stress principle，and analyze the anti-sliding stability subsequently by using pseudo-static approach. Then with the results of calculation，we draw a conclusion that the tunnel will be stable and also present some valuable suggestions.