<p>Seismic demands are prone to concentrate at the corners of RC shear walls, where limited local deformation reduces the effectiveness of conventional dampers. This study introduces a negative stiffness device to decrease the axial stiffness of the wall limb, thereby increasing the working stroke of the wall corner friction damper and improving its energy dissipation efficiency. Frequency domain response based on a SDOF system elucidates the mechanism of the negative stiffness device and further examines its influence on the free vibration behavior governed by Coulomb friction. A mechanical model that accounts for the negative stiffness effect is then established based on a continuous beam model and the principle of energy equivalence. The negative stiffness device effectively lengthens the structural natural period by reducing the effective stiffness. A study of a 12-story benchmark coupled shear wall demonstrates that, under identical design parameters, the negative stiffness friction damping device outperforms the conventional friction damping device in controlling inter-story drift and acceleration, achieving additional reductions of 2.5% in the maximum inter-story drift and 7.9% in the peak top acceleration.</p>