Abstract: Based on the wave theory of fluid-saturated porous media by Biot and the ideal wave theory of fluid media, considering the conditions of fluid-solid coupling of undersea saturated soil and seawater-saturated soil-structure dynamic interaction, using the Hankel function integral transformation method (HFITM), an analytical solution is obtained for the scattering problem of incident P waves for an undersea lining tunnel. The Hankel function integral transformation method can better deal with the surface boundary conditions of half space, avoiding the "big arc assumption" in the traditional researches. Based on the analytical solution, the effects of incident angle and incident frequency of P waves, depth of seawater and buried depth of tunnel on site displacement and stress are calculated and analyzed. The results show that the incident angle of P waves, incident infrequency, depth of seawater and buried depth of tunnel have obvious influences on site displacement and tunnel stress. The horizontal displacement of the site and hydrodynamic pressure of the tunnel increase with the increment of incident angle, and the vertical displacement and total tunnel stress decrease with the increment of incident angle. The tunnel stress decreases significantly with the increase of the incident frequency. The site displacement and tunnel stress are the largest when the water depth is 10 times the tunnel radius. The site displacement and tunnel stress decrease with the increasing buried depth.