A dynamic differential equation of a rub-impact rotor-bearing system with white noise was given to investigate the stochastic bifurcation and chaos behavior of the system. Through numerical integration, achieved the solution of the equation, and analyzed the nonlinear characteristics of the system with the help of the largest Lyapunov exponents, bifurcation diagrams, orbit maps and Poincare maps. It is indicated that the effect of the random disturbance is significant where the response of the rotor system is a quasi-periodic one, nearby periodic one and in bigger rotation speed zone; the greater the random disturbance is, the more significant the influence is when the rotation speed is bigger, and it has certain inhibition to the nonlinear response of the rotor system.