Abstract: The deformation and stability problem on the surrounding rock of underground tunnels group of a large water-conservancy project has been made analyses by BESDAP, a Boundacy Element Static and Dynamic Analysis Program. Considering the some common characters and requirements Of application BEM to large engineering project, several improtant calculating techniques has been treated successfully. The computed results covering the interference each other between various tunnels, the displacements and stresses around tunnels and shear failure region around each tunnel are given. These results and calculating process demonstrate BEMS merits more evidently when it is applied to the surrounding rock analysis of underground tunnels.