Misalignment between driving and driven machines is unavoidable. Flexible couplings are used to accommodate the misalignment. The flexible mechanisms in the coupling impose moments on the rotors connected. The reaction forces developed due to the imposed moments act as periodic excitation forces on the rotating shafts. In the present work the effect of these reaction forces on the vibration characteristics of a two-stage turbine rotor-bearing system has been studied considering flexible element coupling.