Abstract: This study derives the analytical solution for the scattering of plane waves by a cylindrical cavity in a semi-infinite unsaturated porous medium using the wave function expansion method and the Hankel function integral transform method. The primary contribution lies in effectively addressing the orthogonality of boundary conditions at the semi-space surface and the cavity surface with the aid of the Hankel function integral transform method. This enables precise determination of the analytical solutions for surface displacement of the semi-infinite unsaturated porous medium and stress around the cavity. The study thoroughly investigates the effects of medium saturation, incident wave angle, frequency, and cavity burial depth on surface displacement and stress around the cavity. It provides significant theoretical support for analytical research and engineering applications in related fields.