Abstract: Some major achievements in the theoretical study on dynamic characteristics of a high-speed rotor-support-SFD system are reviewed. A practical program to calculate unbalance response of a complex rotor system has been worked out by means of "standard component",and "body information" concepts in the unbalance response prediction research, while the steady, transient and sudden unbalance behaviours of SFD have been comprehensively considered in the dynamic characteristics research. The centralized and uncentralized SFD models are compared, and therefrom a conclusion is drawn that the uncentralized SFD may gain much better damping effect. The design procedure and recommended SFD design parameters from theoretical analysis and practical experience has been verified to be a success.