Abstract: Aiming at the problems of strong mesh dependency and difficulty in simulating transverse joint contact in the seismic analysis of high arch dams using the traditional finite element method， the scaled boundary finite element method （SBFEM） was introduced， and a nonlinear seismic response analysis model for the high arch dam-foundation system was constructed. By combining octree meshing technology and the Lagrange multiplier method， accurate simulation of the contact effects at the dam's transverse joints was achieved by the model. Taking a 300-meter-class high arch dam as an example， the computational results of SBFEM and ABAQUS software were compared and analyzed， and the effectiveness of the model was verified. In addition， the influence of the transverse joint opening effect on the dam's displacement and stress distribution was studied. The results indicated that the dynamic characteristics of high arch dams could be effectively simulated by SBFEM； The stress state of the dam was significantly altered by the presence of transverse joints， causing part of the arch-direction load to be transferred to the cantilever direction.