Abstract: To address the limited understanding of the damage characteristics and the degradation patterns of stiffness and load-bearing capacity of horizontal tails under the cutting action of a discrete rod warhead ring, a finite element model of a controllable discrete rod warhead and an all-moving horizontal tail was established. The damage modes and mechanisms of the horizontal tail under various encounter conditions were analyzed. A stepwise calculation method was used to introduce damage into the mechanical performance assessment of the damaged horizontal tail, and the effects of strike distance and strike position on its stiffness and ultimate load-bearing capacity were investigated. An ultimate load loss coefficient was defined, and damage thresholds were determined in combination with the failure patterns of the damaged horizontal tail under ultimate loading. The results show that, for the selected warhead configuration, the main damage modes of the horizontal tail include airfoil surface deformation, tearing at the joints between the skin and the internal components, continuous cutting damage, and scattered slot-like cutting damage. At short strike distances, the shock wave and rods exhibit a significant coupled damage effect: the shock wave can widen continuous cuts, connect scattered slots, and intensify structural deformation at slot edges. When the strike distance increases from 1.0 m to 1.5 m, the average wingtip displacement under different strike positions decreases from 3.9 cm to 1.7 cm, and the displacement varies approximately linearly with strike position. Under ultimate loading, the damaged horizontal tail exhibits two failure modes: instability in the wing-root region and instability in the damaged region. Among these, instability in the damaged region can serve as a criterion for assessing load-bearing functional damage of the horizontal tail.