Initial defects and working environment will cause different degrees of cracks on the shaft. In order to analyze the effect of cracks on the rotor system, the finite element models of the cracked rotor were established through Jeffcott rotor dynamics model and fracture mechanics theory. The simulation analysis of different crack depths, crack angles and different speeds was carried out, and then a mechanical comprehensive failure table was used to carry out experimental research on part of the cracked rotors. The results show that: the appearance of cracks causes high?order frequency doubling components such as 2X in the vibration response of the system, and the phenomenon of depressions or even ferrules appeared in the axis track, and the vibration amplitude increases accordingly. As the crack deepens, the instability of the system gradually increases. The change of the crack inclination angle also affects the vibration characteristics of the system, and the 45?degree crack has the greatest impact on the system. When the speed starts to increase, the influence of the cracks on the system gradually decreases, the time?domain waveform tends to be stable, and the axis trajectory gradually changes back to an ellipse. Finally, the experimental results were compared with the simulation data to verify the conclusions of simulation and modeling.