Abstract: A mathematical model is presented to study the linear stability of tilting-pad journal bearing system. By employing the Newton-Raphson method and the pad assembly technique, the full dynamic coefficients involving the shaft degrees of freedom as well as the pad degrees of freedom are obtained. Based on these dynamic coefficients, the perturbation equations including self-excited motion of the rotor and rotational motion of the pads are established. Through analyzing complex eigenvalues depending on these differential equations, it is easy to determine the pad critical mass and damping ratio used to exam the stability of the system. The computing results show that some factors, such as preload coefficient, pivot position and rotor speed, significantly affect the stability of tilting-pad journal bearing system. Reasonable selection of the parameter values is helpful to enhance the stability threshold of the system.