In this paper, viscoelastic insulators are employed into an automotive brake system to improve the vibration stability. Thus, the system stability has been considered with hypothesis of couple modes. Therefore, the originality of the paper includes the complex eigenvalue analysis of viscoelastic model in brake squeal phenomenon. Accordingly, the brake system is simulated in a FEM code and then, the viscoelastic materials are applied using Negami-Havriliak model. Comparing the eigenvalue results in both cases, in which the viscoelastic material is treated as an absorber at the first case and without treatment for another case, indicates an improvement in instability mode at 12 kHz. In addition, applying these absorbers has no significant effects in low frequency. Furthermore, comparison of the results presented here with experimental ones done by other author, indicates the reliability of the presented model. Finally, with applying the strain energy analysis, the location of absorber treatment as well as its optimum thickness is concluded.