Abstract: In order to verify the stability and rock cover of Xiamen subsea tunnel which is under design now. According to coupled fluid-mechanical theorem, FLAC^3D （Fast Lagrangian Analysis of Continua in 3 Dimensions） numerical analysis for 4 profiles has been done along the longitudinal of the tunnel. Based on original design of the tunnel, rock covers with a decrease of 4 m is considered in the numerical simulations. From the numerical results of stress distribution, displacements,plastic zones of rock mass and pore-pressure distributions after excavation with rock cover decreasing 4 m,it can be concluded that the tunnel is stable even the rock cover of the subsea tunnel decreases 4 m compared to the original design elevation. Some conclusions are obtained which are useful for the future construction and other rock engineering.