Abstract: Based on the nonlinear dynamical model of the rotor-bearing system with rub-impact fault, the stability of the periodic motion of the system in unbalance-rotational speed and clearance-rotational speed plane were studied by the continuation-shooting algorithm for the periodic solutions of nonlinear non-autonomous dynamic systems. The stability of the periodic motion of the system decreases obviously when the unbalance increases. The small unbalance results in Hopf bifurcation, and the large unbalance results in doubling bifurcation. The critical speed of period doubling bifurcation increases when the clearance between rotor and stator decreases because rub-impact affects, the occurrence of oil whirl, and it does not change under large clearance because the oil whirl occurs before rub-impact or the rub-impact does not occur.