Abstract: To solve the problem of unstable vibration occurring in the HP-IP rotor of a 660 MW supercritical steam turbine, a dynamic response model was set up for the system under coupled action of shaft bend and rotor unbalance using finite element method, of which the accuracy was verified with field experiments. Results show that the shaft bend caused by inconsistency between balancing and unbalance plane can not be neglected at high rotating speeds, since it may lead to the instability and increase of vibration. The balancing plane should be chosen on the unbalance plane as far as possible. High-pressure rotor is easy to have creep deformation under the effect of external force due to its high-temperature operation environment; the phenomenon is even more obvious for high-pressure rotors of large steam turbine.