A series solution of two-dimensiona1 scattering of Plane SH waves by a circular inclusion in an infinite strip region is presented using the wave functions expansion. The Solution is reduced to solving a set of infinite linear algebraic equations using the interior region form of Graf’s addition theorem. Numerical solutions are obtained by truncation of the infinite equations and the accuracy is ensured by the extent to which the numerica1 results fit the exact boundary conditions with the increasing of the truncation order. Finally, the dynamic stress concentration factors around the circular inclusion are discussed to the cases of different thickness of strip region and geometry location of circular inclusion in numerical examples. The calculating results show that the existence of free boundary of strip region has great effect on incident plane SH-wave, and the variation of thickness of the infinite strip region can remarkably change the dynamic behavior of circular cavity.