To suppress the brake noise of automotive disc brake systems, a reliability analysis method of vibration stability for brake systems is presented. The method is mainly based on the theories of reliability analysis, Monte Carlo method and RSM (Response Surface Method). In the proposed method, random parameters and interval parameters are introduced to describe the uncertainties of a brake system. Response surface approximation models of the unstable eigenvalue are created by RSM, then the global sensitivities of uncertain parameters are calculated by Sobol' method, and reliabilities of the brake system vibration stability are analyzed using Monte Carlo method. An analysis of a float caliper disc brake system is carried out by using the proposed method, the reliabilities of system stability and global sensitivities of uncertain parameters are obtained, some measures to improve the brake system vibration stability are suggested from a reliability point of view. The applicability of traditional research methods is improved and higher reference values are provided in practical engineering, through the introduction of uncertainty analysis techniques.