Abstract: The non-synchronous vibration (NSV) of compressor rotor blades is a new type of aeroelastic problem discovered in recent years, the characteristics is manifested as the non synchronization between the vibration frequency and the rotating frequency and exhibiting frequency locking phenomena, which seriously affects the reliability and operation safety of aeroengine. Currently, the mechanism is not fully understood. In order to deeply investigate the interaction mechanism between the unstable flow and non-synchronous vibration of blades, a time domain fluid-structure interaction method of multistage compressor full-annulus rotor blades was established, the unsteady flow field, aerodynamic excitation frequency and structural response characteristics of rigid and flexible blades were numerically studied to reveal the fluid-structure interaction mechanism of NSV. The results indicate that the periodic shedding and reattachment process of radial separation vortices on the tip suction surface causes the severe pressure fluctuation under near stall conditions. Its three times harmonic aerodynamic excitation frequency is close to the first-order bending natural frequency and provides the initial aerodynamic excitation for the NSV. During the NSV, the displacement response of rotor blade exhibits equal amplitude limit cycle oscillation, and dominated by the first-order bending model. The non-integer multiple aerodynamic excitation and its harmonic frequencies generated by radial separation vortex are ultimately locked-in the first-order bending natural frequency. The motion stress of NSV causes the circumferential flow field of adjacent channels to become consistent. This present result and the mechanism understanding of fluid-structure interaction of NSV can provide useful references for the analysis of blade vibration failure induced by unstable flow in compressor.