Abstract: To solve the problem of exssive shafting vibration appearing at bearings 3, 4 and 5 for IP/LP rators in a 1 000 MW steam turbine with single supports, a dynamic finite element model was set up, so as to analyze the sensitivity of vibration of all bearings to the unbalance excited on the coupling connecting two low-pressure rotors. Moreover, the dynamic coefficient of bearing 4 between two LP rators was altered by changing its inlet oil temperture, thus to study the effects of dynamic coefficient on the steady state response of the shafting. Results show that the dynamic coefficient of bearing 4 has the greatest influence on the vibration of bearing 5, followed by bearing 4, which are for supporting of LP rator 2; whereas the dynamic coefficient of bearing 4 has little influence on the vibration of bearing 1 and 2 for the HP rator. The excessive shafting vibration could be reduced by improving the inlet oil temperature of bearing 4 in actual applications.