In order to analyze the local rubbing bifurcation and the chaotic dyna mic behavior of a rotor testbed and find out routes to the chaos, this paper s e t up a motion differential equation of dualdisc overhung rotor system, force m odels of coulomb friction and noncoulomb friction were employed respectively. B y using the numerical integration method, based on speed parameters for the bifu rcation, the system motion state was studied through the Poincare map, wave form graph, phase plan graph, chart of axes track, power spectrums, and the autoco r relation function method. The results show that the ranges and widths of the rot or speeds resulting in the bifurcation are obviously different for the two frict ion models, and the routes to chaos are mainly intermittence chaos and period bi furcations. The simulation results correspond with the experimental ones .It is concluded that the calculated results by using the nonCoulomb friction model a re more consistent with the actual situation than the Coulomb friction model.