When the crack and rub-impact coexist in the rotor system, nonlinear behaviors of the system become more complex. In light of this problem, the rotor crack faults are analyzed and diagnose. First, the dynamic model of crack and the rub-impact rotor is established, a diagnosis method of crack fault is proposed based on the change of morphological characteristics of axis orbits in multiple faults. The morphological characteristics of axis orbits are analyzed around the 1/2 subcritical speed zone. The results show that the shapes of inner loops are changed and the offset direction of inner loops rotates a certain angle in the neighborhood of 1/2 subcritical speed. Axis orbits around the 1/2 subcritical speed zone are evidently different between the crack and rub-impact rotor and the rub-impact rotor. Then, the analysis of morphological characteristics of axis orbits provides a simple and novel method for the preliminary diagnosis of crack fault in the multi-fault rotor system, which improves the efficiency of fault diagnosis. Meanwhile, the dynamic response of different rotor systems is analyzed by the bifurcation and frequency spectra. Finally, the experiments are conducted on Bently rotor test rig to verify the simulation results of the crack rotor system.