Abstract: In terms of Biot’s dynamic theory,the multi-polar coordinate and complex function were used to put forward an approximate analysis method for scattering and dynamic stress concentration of steady SV wave around a circular cavity in half space of saturated soil,where a circular cavity with large radius was used to replace the straight boundary of the half space of saturated soil.By using the theory of Helmholtz,the general solution of the Biot’s wave function was given and a system of infinite linear algebraic equations of the problem studied in this paper could be given by means of the complex series expansion technology and the boundary conditions of the solid matrix and the fluid.Then the variation of the coefficient of dynamic stress concentration at boundaries of the cavity was discussed with different parameter conditions.The results of the given example indicated that the method used in this paper was useful and efficient to the scattering and dynamic stress concentration of shear waves in which the straight boundary existed.