Abstract: Dense matrix equations greatly weaken the advantages of traditional boundary element methods for solving large scale practical engineering problems. Therefore, combined with the fast multipole expansion technique, a new rapid indirect boundary element method is developed for solving large scale or high frequency elastic wave scattering problems. Taking the scattering of an SH wave around a cavity as an example, the detailed solution process of FMM-IBEM is presented. It is verified that this method greatly improves computing speed and reduces storage requirements, meaning that elastic wave scattering problems with millions of DOF’s can be solved effectively and accurately on an ordinary personal computer. Finally, a high frequency scattering problem involving an SH wave scattered by a canyon in elastic half space is solved, and some important characteristics of the high frequency wave scattering are discussed based on the numerical results, which can provide a theoretical basis for seismic design of large engineering projects located in canyons.