This paper comprehensively analyzes the effect of key operation parameter differences on the rotor dynamic characteris tics of the turbine-generator under the FISC. The key operation parameters include short degree， short position and generator load rate. The rotor’s dynamic characteristics include rotor unbalanced magnetic pull （UMP） excitation characteristics， radial vibration response characteristics and rotor core dynamics response laws. This paper explores the difference in rotor dynamic characteristics acting under different operation parameters based on the theoretical analysis of UMP excitation and vibration response of flexible ro tors， finite element simulation calculation and experiment verification. It is shown that the rotor UMP closes to zero in normal con ditions， and the rotor vibration is dominated by conventional fundamental frequency and the even frequency doubling transmitted by the stator. The rotor UMP and its vibration response will produce a new odd-harmonic order component， and the amplitude of pass band vibration will also be increased. As the short degree or load increases， the amplitude of the fundamental frequency of the UMP and vibration response will be increase. Besides， the closer the short position is to the big tooth， the bigger the amplitude of the UMP and vibration response will be. The most dangerous of the dynamic response positions are located at the outer surface and the inner slot surface edge of the big tooth.