Abstract: The scattering of a semi-cylindrical canyon and a crack with incident SH waves was studied based on Greens function. A special Greens function which was a fundamental solution of displacement field for a half-elastic space with a semi-cylindrical canyon bearing an anti-plane harmonic line-source force at any point was proposed for the present problem. And the scattering problem of SH-wave by a half-elastic space with semi-cylindrical canyon was solved. Then, at the actual position of cracks, the existent cracks could be reverted by using Greens function and the method of crack-division. Integration for the obtained solution of the whole problem was established, and the solution of the ground surfaces displacement amplitude was concluded.