Abstract: The indirect boundary element method is used to study the 3D wave scattering problem of obliquely incident plane P1 waves by an alluvial valley embedded in a fluid-saturated,layered half-space in frequency domain,based on the given 3D exact dynamic stiffness matrix and Green’s functions of moving distributed loads in a fluid-saturated,layered half-space. The method has the advantage that fictitious moving distributed loads and pore pressure can be acted directly on the interface of the valley and the layered half space without singularity. The rationality of the method is validated by comparing with known results,and the numerical analyses are performed by examples of a valley embedded in a fluid-saturated half space and in a single fluid saturated soil layer over elastic bedrock. It is shown that the 3D scattering is essentially different from the 2D case and the parameters such as incident angle,porosity,layer stiffness and layer thickness,etc. have significant effect on the dynamic responses near the valley.