Taking the high-grade K21 segmental rock slope in Zixing Expressway as the research object, a numerical model is built on the typical slope in the study area to simulate the excavation and supporting process of the slope by using on-site investigations, numerical simulation methods. Its stability, displacement, stress and strain features under different excavation and supporting are analyzed and summarized. The rationality of the excavation and support design and the safety of the slope reinforcement are verified. The stress-strain laws of the slope in the excavation and support process are analyzed. The results show that the main manifestation of disturbance in excavation of bedding rock slope is that the excavation destroys the original stress distribution of the slope, causes cracks and deformations in the rock mass and gradually expands, and weakens the strength of the rock and its stratum. Simultaneously, the open-cut cutting of the rock slope produces a free surface and directly destroys the original continuous force system of the slope. Due to the low shear strength of the weak layer, the overall rock formations slide along the weak structural surface which exposed by slope excavation. On one hand, the anchor cable frame increases the stability of the slope by controlling the displacement of the slope body. On the other hand, the layered rock mass is anchored together by the prestressed anchor cable, so that the frictional resistance between the layers increases. The stress and deflection are greatly reduced, which improves the shear strength of the layer greatly.