Abstract: Taking a fourspan shaft rotor system that composes of big gear， turbine， mediumpressure and lowpressure cylinder rotor at the low pressure side of a large compressor as the research object， FEM was used to establish the system dynamic model and unbalance dynamic matching of the whole system was implemented via two kinds of optimization method. The simulation results showed that parameters such as unbalance mass and phase have achieved two good combinations， which are suitable for different matching conditions. The unbalance response namely the vibration of the whole system was reduced. Dynamic performance and resistance of unbalance fault were enhanced effectively. Feasibility of the dynamic matching technology applied to the whole multispan rotor system is verified.

Key words: multispan rotor, finite element method(FEM), unbalance, dynamic matching, optimization