Abstract: Dynamics analysis and parameters optimization of rotor-bearing system provide a foundation for the design of high speed rotational machines. Finite element analysis (FEA) model of a flexible rotor-bearing system was built with FEA software. Both the stability and critical response problems were solved. Based on APDL language and particle swarm algorithm, multi-objective optimization programs were developed. All the bearing parameters and the journal diameter were optimized. Considering the results of both stability optimizaiton and critical response optimization, it is proposed that the stability optimization results should be adopted during a high speed operation of the rotor and the bearing parameters should be adjusted according to the critical response optimization result.