With the aim to study the mechanical properties of the mixed-flow pump impeller rotor under the fluid-structure interaction, the flow field and impeller structure response in the mixed-flow pump were cooperatively solved based on the bidirectional synchronization solving method. The Reynolds-averaged Navier-Stokes equations and k-ε turbulent model were used for the simulation of the flow field, while the elastic structural dynamics equations were used for the structural dynamic response. The influence before and after fluid-structure interaction on the flow field in the mixed-flow pump was studied by comparison of pressure fluctuation and external characteristic changes at different monitoring points between flow channels. Meanwhile, the deformation of blade and the dynamic stress distribution on blade were analyzed based on the bidirectional fluid-structure interaction. The results showed that fluid-structure interaction had greater influence on the pressure pulsation amplitude at the vane outlet. After the coupled interaction, the amplitude of the head and power fluctuation were increased while the efficiency was decreased. The largest deformation location of blade occurred at the back side near to the rim of impeller with the maximum deformation of 0.062 7 mm. The maximum equivalent stress was detected on the back side nearby the outlet of the hub with the maximum equivalent stress of about 19.85 MPa. The coupling dynamic stress of the sample point was changed periodically and the amplitude value of the dynamic stress on the rim and the hub had a difference by 10 3 magnitudes, which meant that fatigue damage was easier to happen in the hub region. The results of the research provide reference basis for the structure design and reliability analysis of the mixed-flow pump.