The damping of the primary structure has a certain impact on the dynamic characteristics of the system. However, the damping of the primary structure is often neglected when optimizing the design of DVAs using analytical methods to simplify calculations. This paper employs the perturbation method to derive an analytical solution for the optimized design parameters in negative stiffness-inerter dampers considering the damping of the primary structure under random excitation. Firstly, the governing equation of the vibration system under base acceleration excitation is established to obtain the absolute acceleration response transfer function and the corresponding mean square value. Secondly, the perturbation method is introduced to obtain the analytical solution of the optimal design parameters of the negative stiffness-inerter damper considering the primary structure damping under the H₂ criterion, and the validity of these analytical solutions is verified. Subsequently, through comparative case studies, it is demonstrated that neglecting the primary structure damping can cause significant deviations between the optimal design parameters of the negative stiffness-inerter damper and the actual values when the primary structure damping radio is relatively large highlighting the necessity of considering primary structure damping in parameter analytical optimization design. Finally, the optimal mean square value of absolute acceleration in the frequency domain and the peak value of the time history response in the time domain are compared after installing negative stiffness-inerter dampers and inerter dampers for the primary structure with damping, respectively. The result indicates that reducing the damping ratio of the main structure allows negative stiffness to increasingly improve the damper’s effectiveness. Furthermore, it demonstrates that the negative stiffness-inertance damper is more efficient in controlling the peak time-history response of the main structure.