Abstract: A mathematical model of rubbing and impact for a nonlinear rotor-box isproposed in the paper. By means of numerical simulation,bifurcation diagrams are obtained under different systemparameters. Meanwhile, the effect of the different system parameters on thebifurcation is analyzed in the numericalsimulation. Poincare mappings are given on relevant system parameters andfrequencies. Finally, the effect of the different system parameters on therub-impact characteristics of the nonlinear rotor-box system isdiscussed. Thevariation of the eccentricity may influence chaotic motions and bifurcationphenomena and an increase of damping causes a gradual reduction of thechaotic bands, but an increase of rub-impact stiffness increases the chaotic bandsand causes a complex motion.