[en] A pad-on-disc frictional model, a rotating disc under acted by a pad, is established. The moving interaction between the coupled pad and disc is estimated using the Stribeck-type friction model, and the partial differential equation of the disc vibration is calculated using the finite difference method with moving load simulation procedure. Bifurcation diagram and phase portraits of the pad motion with 3-DOFs reveal that as the rotating speed is below a critical value, instability happens and stick–slip vibration is resulted for the pad. Then, eigenvalue analysis is applied to evaluate stability of the pad considering stochastic variation of frictional coefficients and contact effect. Probability distribution diagrams are presented to show that the higher initial displacement of preload or friction coefficient can bring occurrence of more probably instability in uncertain state.