The tribological mechanisms of nanotwinned copper (NT-Cu) exhibit significant complexity and diversity during prolonged friction processes. By combining tribological theory with experimental analysis, a finite element model was developed to simulate the evolution of wear morphology and surface stress. Results indicate that as friction duration increases, the dominant wear mechanism of NT-Cu transitions from abrasive wear in the initial stage (60   s) to a composite form involving fatigue, delamination, and oxidation. Following 600   s of sliding, a third body layer forms on the friction surface, which then undergoes cyclic formation and spallation with continued sliding. This dynamic process not only induces delamination wear but also reduces direct contact with the counterpart, thereby partially suppressing the wear of NT-Cu. Furthermore, it was observed that under cyclic stress, fatigue cracks propagate perpendicular to the friction direction, a behavior closely associated with the distribution of internal shear stress in the material. These findings provide deeper insights into the friction-induced damage mechanisms of nanotwinned metals.