To investigate the load-bearing characteristics of lightweight surface-mounted slewing cable anchorage, this paper takes the Yellow River Three Gorges Bridge project as an example, establishing a nonlinear finite element model and verifying its effectiveness through a 1:100 scale physical model test. Furthermore, a theoretical stability analysis model was established to quantify the contributions of base friction and toothed block clamping action. By analyzing displacement behavior, rock mass shear characteristics, and plastic zone evolution, the combined load-bearing mechanism was revealed. The results show that the anchorage system begins to destabilize when the load reaches 18P. Both numerical and theoretical analyses confirm that the toothed blocks significantly improve the stability of the anchorage system; the safety factor increases from 6.84 considering only friction to 16.59 considering clamping action, which is consistent with the 17P plastic threshold observed in the simulation. Rock mass resistance is generated from bottom to top, providing passive resistance through shear action. The final determined failure mode is the interconnection of local plastic zones and the overturning failure of the anchorage system.