Abstract: Soil arching effect of core wall could reduce its vertical stress and induce horizontal fractures, resulting in hydraulic fracturing that threatens dam safety, and this is particularly significant in high core-wall rockfill dams. This study has focused on a 300 m high-grade core-wall rockfill dam. We herein analyze the stress in the dam body and its settlement trend using FEM simulations and monitored data, then discuss the effects of dam materials on the core wall and the locations with severe soil arching effect. Finally, we evaluate the possibility of hydraulic fracturing caused by soil arching and describe how the stress transfer in core wall varies vertically with elevation. Results show that the largest settlement of core wall calculated by FEM is slightly smaller than the monitored value, and no tensile stress in the dam was observed. On the base of core wall the arching effect is obvious in the downstream, while above the base it can be obviously observed only near the dam axis but not strong enough to cause hydraulic fracturing. Generally, the arching effect is greatly influenced by the elastic modulus ratio of core wall over dam shell and the Poisson's ratio of core wall. Above elevation 780 m, the soil arching effect is quite severe, causing a greater reduction in top-down stress transfer.