Experiment rig of rotor coupling bearing isolator system was installed to simulate marine steam turbine geared unit and its isolation system,the bearing elevation adjustor and unbalance mass were used to model the misalignment trouble of this unit,the characteristics of static and dynamic misalignment trouble and low frequencylocking trouble were studied,and the solutions to those troubles were also provided.Experiment research results show,for rotor coupling bearing system with isolators,both the static misalignment and unbalance force due to dynamic misalignment will lead 2X basic frequency.When the basic frequency arrives to the natural frequency of isolator system,two main frequencies appear,basic frequency and locked low frequency,and the structure of this system becomes unstable, which causes quasiperiodic bifurcation.Frequencylocking trouble would threaten safe and stable operation of rotor system seriously.The above research results will provide practical basis for misalignment and frequencylocking trouble and stable theoretical analysis of marine steam turbine geared unit and its isolation system.