Abstract: The scattering and diffraction of plane Rayleigh waves in circular alluvial valleys with soft soil deposits was studied with the deposits simulated by saturated porous medium of Biot dynamic theory,and the half space assumed to be elastic single-phase mediam.The expansion technique of Fourier-Bessel series was used to solve this problem.The results of amplitudes of surface displacement were presented,and the effects of frequency and the stiffness of the valley were discussed for soft and harden alluvial valleys.