Nonlinear dynamical characteristics of rub-impact rotor system with fractional order damping are investigated.The model of rub-impact comprises a radial elastic force and a tangential Coulomb friction force.The fractional order damped rotor system with rubbing malfunction is established.The four order Runge-Kutta method and ten order CFE-Euler methods are introduced to simulate the proposed fractional order system equations.The effects of the rotating speed ratio, derivative order of damping and mass eccentricity on the system dynamics are investigated using rotor trajectory diagrams, bifurcation diagrams and Poincare map.Various complicated dynamic behaviors and types of routes to chaos are found, including period doubling bifurcation, sudden transition and quasi-periodic from periodic motion to chaos.The analysis results show that the fractional order rub-impact rotor system exhibits rich dynamic behaviors, and that the significant effect of fractional order will contribute to comprehensive understanding of nonlinear dynamics of rub-impact rotor.