<p>The soil arching effect is an important factor affecting the internal load transfer of excavation-induced slopes. Physical model tests are usually used for studying the soil arching effect. Although physical model tests can monitor local point loads to demonstrate changes in local stresses, changes in force chains inside slopes are rarely demonstrated by physical modelling, which restricts the understanding of load transfer. To explore overall changes in stresses in slopes from a more microscopic perspective, a numerical simulation of the slope under excavation was carried out. Using built-in code and fish function programming in PFC^3D, the slope model was developed. Monitoring areas were set up to monitor the changes in stresses and force chains during excavation. The simulation results show that excavation width affects the size of deformation area, and the deformation area expands as excavation width increases. Excavation causes load transfer and the formation of soil arching in the slope. A mechanism is proposed to explain the effect of excavation on soil arching formation and load transfer. The numerical simulation is important for revealing the load transfer of slopes during excavation, and the research results have practical value for the prevention and mitigation of landslides caused by excavation.</p>