It cannot reflect the real situation for analysis of flexible coupling-rotor system if the flexible coupling is viewed as shaft or directly ignored. After carefully analyzing the responses in different speed and different unbalance displacements considering the threaded coupling, the accurate threaded coupling-rotor system is established using finite element method. Meanwhile, the threaded coupling-rotor system with rubbing failure is also analyzed in this paper. The results show that the flexible couplings has obvious effect on the vibration characteristics of the failure rotor system. The flexible coupling will play a more important role at high rotational speed.